A non-technological, repeating, phenomenon in the sky, holding its position in the sky for hoursA world with a moon orbiting much closer than oursMaking Mars biggerCould two stars of equivalent mass/size form a binary system and be different colors?What astronomical considerations are necessary for the planet in this model to possibly be Earth-like?How would a torus world (donut shaped) have to rotate in order to have a stable day / night cycle in all of its regions?Could I have an earth-like planet from which sun and moon would never be simultaneously visible?Describing a planet on a comet like orbitWhat is the maximum orbital time for my moon around my planet?What are the day and night fluctuations for a moon orbiting a planet the size of Jupiter?Designing a super-comfortable Earth analog

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A non-technological, repeating, phenomenon in the sky, holding its position in the sky for hours


A world with a moon orbiting much closer than oursMaking Mars biggerCould two stars of equivalent mass/size form a binary system and be different colors?What astronomical considerations are necessary for the planet in this model to possibly be Earth-like?How would a torus world (donut shaped) have to rotate in order to have a stable day / night cycle in all of its regions?Could I have an earth-like planet from which sun and moon would never be simultaneously visible?Describing a planet on a comet like orbitWhat is the maximum orbital time for my moon around my planet?What are the day and night fluctuations for a moon orbiting a planet the size of Jupiter?Designing a super-comfortable Earth analog






.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty
margin-bottom:0;

.everyonelovesstackoverflowposition:absolute;height:1px;width:1px;opacity:0;top:0;left:0;pointer-events:none;








20














$begingroup$


Is this physically possible?



A non-technological phenomenon visible in the same position of the sky, for 18 hours of a day using the other 6 to do whatever, rise and set, just be impossible to see, it doesn't matter.



What matters is the 18 hours of constant position in the sky, on a repeating cycle.



For an observer that is assumed to be watching from the same place, each cycle.



The viewer's planet is not Earth, just has enough similarities for humans to live on it.




If it is possible, how complex a system would I need to make such a thing happen, and how stable would that system be?



The cause can be in the atmosphere, as long as it cycles, and has the same visibility.



I'd like planets, but if that's not possible, then use whatever is possible.










share|improve this question











$endgroup$






This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.











  • 1




    $begingroup$
    Does it have to be visible from everywhere on earth at some point (or at least, all around some great circle of the earth's surface), or is having it only visible from one part of the globe acceptable?
    $endgroup$
    – Starfish Prime
    Apr 28 at 19:08











  • $begingroup$
    @StarfishPrime - Observer of single position. Can you help me think of how to add that into the title, while not going over 150 characters?
    $endgroup$
    – Malady
    Apr 28 at 19:13







  • 3




    $begingroup$
    What does "int the same position for 18 hours a day" mean? Is it in the same position with respect to the fixed stars? Or is it immobile, that is, it does not rise and does not set, and in this case what happens during the other 6 hours? Must it be visible in daylight? What does "in the sky" mean? In outer space, or is an object flying in the atmosphere acceptable?
    $endgroup$
    – AlexP
    Apr 28 at 19:21







  • 1




    $begingroup$
    This is an interesting question, but so far all the comments are asking for clarifications which indicates to me you're not exactly clear what it is you're asking. I've voted to put your question on hold until you edit it. If you clarify before it actually gets closed, I'll happily retract the VTC!
    $endgroup$
    – elemtilas
    Apr 28 at 19:38






  • 2




    $begingroup$
    Keep the title short; put all the "stuff" in the query body.
    $endgroup$
    – elemtilas
    Apr 28 at 19:45

















20














$begingroup$


Is this physically possible?



A non-technological phenomenon visible in the same position of the sky, for 18 hours of a day using the other 6 to do whatever, rise and set, just be impossible to see, it doesn't matter.



What matters is the 18 hours of constant position in the sky, on a repeating cycle.



For an observer that is assumed to be watching from the same place, each cycle.



The viewer's planet is not Earth, just has enough similarities for humans to live on it.




If it is possible, how complex a system would I need to make such a thing happen, and how stable would that system be?



The cause can be in the atmosphere, as long as it cycles, and has the same visibility.



I'd like planets, but if that's not possible, then use whatever is possible.










share|improve this question











$endgroup$






This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.











  • 1




    $begingroup$
    Does it have to be visible from everywhere on earth at some point (or at least, all around some great circle of the earth's surface), or is having it only visible from one part of the globe acceptable?
    $endgroup$
    – Starfish Prime
    Apr 28 at 19:08











  • $begingroup$
    @StarfishPrime - Observer of single position. Can you help me think of how to add that into the title, while not going over 150 characters?
    $endgroup$
    – Malady
    Apr 28 at 19:13







  • 3




    $begingroup$
    What does "int the same position for 18 hours a day" mean? Is it in the same position with respect to the fixed stars? Or is it immobile, that is, it does not rise and does not set, and in this case what happens during the other 6 hours? Must it be visible in daylight? What does "in the sky" mean? In outer space, or is an object flying in the atmosphere acceptable?
    $endgroup$
    – AlexP
    Apr 28 at 19:21







  • 1




    $begingroup$
    This is an interesting question, but so far all the comments are asking for clarifications which indicates to me you're not exactly clear what it is you're asking. I've voted to put your question on hold until you edit it. If you clarify before it actually gets closed, I'll happily retract the VTC!
    $endgroup$
    – elemtilas
    Apr 28 at 19:38






  • 2




    $begingroup$
    Keep the title short; put all the "stuff" in the query body.
    $endgroup$
    – elemtilas
    Apr 28 at 19:45













20












20








20


2



$begingroup$


Is this physically possible?



A non-technological phenomenon visible in the same position of the sky, for 18 hours of a day using the other 6 to do whatever, rise and set, just be impossible to see, it doesn't matter.



What matters is the 18 hours of constant position in the sky, on a repeating cycle.



For an observer that is assumed to be watching from the same place, each cycle.



The viewer's planet is not Earth, just has enough similarities for humans to live on it.




If it is possible, how complex a system would I need to make such a thing happen, and how stable would that system be?



The cause can be in the atmosphere, as long as it cycles, and has the same visibility.



I'd like planets, but if that's not possible, then use whatever is possible.










share|improve this question











$endgroup$




Is this physically possible?



A non-technological phenomenon visible in the same position of the sky, for 18 hours of a day using the other 6 to do whatever, rise and set, just be impossible to see, it doesn't matter.



What matters is the 18 hours of constant position in the sky, on a repeating cycle.



For an observer that is assumed to be watching from the same place, each cycle.



The viewer's planet is not Earth, just has enough similarities for humans to live on it.




If it is possible, how complex a system would I need to make such a thing happen, and how stable would that system be?



The cause can be in the atmosphere, as long as it cycles, and has the same visibility.



I'd like planets, but if that's not possible, then use whatever is possible.







planets hard-science






share|improve this question















share|improve this question













share|improve this question




share|improve this question



share|improve this question








edited Apr 29 at 23:52







Malady

















asked Apr 28 at 19:01









MaladyMalady

2,1811 gold badge13 silver badges46 bronze badges




2,1811 gold badge13 silver badges46 bronze badges





This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.








This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.






This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.









  • 1




    $begingroup$
    Does it have to be visible from everywhere on earth at some point (or at least, all around some great circle of the earth's surface), or is having it only visible from one part of the globe acceptable?
    $endgroup$
    – Starfish Prime
    Apr 28 at 19:08











  • $begingroup$
    @StarfishPrime - Observer of single position. Can you help me think of how to add that into the title, while not going over 150 characters?
    $endgroup$
    – Malady
    Apr 28 at 19:13







  • 3




    $begingroup$
    What does "int the same position for 18 hours a day" mean? Is it in the same position with respect to the fixed stars? Or is it immobile, that is, it does not rise and does not set, and in this case what happens during the other 6 hours? Must it be visible in daylight? What does "in the sky" mean? In outer space, or is an object flying in the atmosphere acceptable?
    $endgroup$
    – AlexP
    Apr 28 at 19:21







  • 1




    $begingroup$
    This is an interesting question, but so far all the comments are asking for clarifications which indicates to me you're not exactly clear what it is you're asking. I've voted to put your question on hold until you edit it. If you clarify before it actually gets closed, I'll happily retract the VTC!
    $endgroup$
    – elemtilas
    Apr 28 at 19:38






  • 2




    $begingroup$
    Keep the title short; put all the "stuff" in the query body.
    $endgroup$
    – elemtilas
    Apr 28 at 19:45












  • 1




    $begingroup$
    Does it have to be visible from everywhere on earth at some point (or at least, all around some great circle of the earth's surface), or is having it only visible from one part of the globe acceptable?
    $endgroup$
    – Starfish Prime
    Apr 28 at 19:08











  • $begingroup$
    @StarfishPrime - Observer of single position. Can you help me think of how to add that into the title, while not going over 150 characters?
    $endgroup$
    – Malady
    Apr 28 at 19:13







  • 3




    $begingroup$
    What does "int the same position for 18 hours a day" mean? Is it in the same position with respect to the fixed stars? Or is it immobile, that is, it does not rise and does not set, and in this case what happens during the other 6 hours? Must it be visible in daylight? What does "in the sky" mean? In outer space, or is an object flying in the atmosphere acceptable?
    $endgroup$
    – AlexP
    Apr 28 at 19:21







  • 1




    $begingroup$
    This is an interesting question, but so far all the comments are asking for clarifications which indicates to me you're not exactly clear what it is you're asking. I've voted to put your question on hold until you edit it. If you clarify before it actually gets closed, I'll happily retract the VTC!
    $endgroup$
    – elemtilas
    Apr 28 at 19:38






  • 2




    $begingroup$
    Keep the title short; put all the "stuff" in the query body.
    $endgroup$
    – elemtilas
    Apr 28 at 19:45







1




1




$begingroup$
Does it have to be visible from everywhere on earth at some point (or at least, all around some great circle of the earth's surface), or is having it only visible from one part of the globe acceptable?
$endgroup$
– Starfish Prime
Apr 28 at 19:08





$begingroup$
Does it have to be visible from everywhere on earth at some point (or at least, all around some great circle of the earth's surface), or is having it only visible from one part of the globe acceptable?
$endgroup$
– Starfish Prime
Apr 28 at 19:08













$begingroup$
@StarfishPrime - Observer of single position. Can you help me think of how to add that into the title, while not going over 150 characters?
$endgroup$
– Malady
Apr 28 at 19:13





$begingroup$
@StarfishPrime - Observer of single position. Can you help me think of how to add that into the title, while not going over 150 characters?
$endgroup$
– Malady
Apr 28 at 19:13





3




3




$begingroup$
What does "int the same position for 18 hours a day" mean? Is it in the same position with respect to the fixed stars? Or is it immobile, that is, it does not rise and does not set, and in this case what happens during the other 6 hours? Must it be visible in daylight? What does "in the sky" mean? In outer space, or is an object flying in the atmosphere acceptable?
$endgroup$
– AlexP
Apr 28 at 19:21





$begingroup$
What does "int the same position for 18 hours a day" mean? Is it in the same position with respect to the fixed stars? Or is it immobile, that is, it does not rise and does not set, and in this case what happens during the other 6 hours? Must it be visible in daylight? What does "in the sky" mean? In outer space, or is an object flying in the atmosphere acceptable?
$endgroup$
– AlexP
Apr 28 at 19:21





1




1




$begingroup$
This is an interesting question, but so far all the comments are asking for clarifications which indicates to me you're not exactly clear what it is you're asking. I've voted to put your question on hold until you edit it. If you clarify before it actually gets closed, I'll happily retract the VTC!
$endgroup$
– elemtilas
Apr 28 at 19:38




$begingroup$
This is an interesting question, but so far all the comments are asking for clarifications which indicates to me you're not exactly clear what it is you're asking. I've voted to put your question on hold until you edit it. If you clarify before it actually gets closed, I'll happily retract the VTC!
$endgroup$
– elemtilas
Apr 28 at 19:38




2




2




$begingroup$
Keep the title short; put all the "stuff" in the query body.
$endgroup$
– elemtilas
Apr 28 at 19:45




$begingroup$
Keep the title short; put all the "stuff" in the query body.
$endgroup$
– elemtilas
Apr 28 at 19:45










13 Answers
13






active

oldest

votes


















55
















$begingroup$

It's physically possible.



Put a spherical object in a geostationary orbit, make it rotate about its own axis at a rate suited to your own visibility/non-visibility requirements, and make a portion of it have very low albedo.



Staying at a single point in the sky, the object will only be visible while the higher albedo portion is facing the planet and become invisible while the low albedo portion rotates into view.



It could technically happen by chance but would only be stable for as long as the orbit is stable, which really depends on your planetary system.






share|improve this answer










$endgroup$










  • 4




    $begingroup$
    Difficult to imagine another possible answer. +1
    $endgroup$
    – 011358 smell
    Apr 28 at 20:16






  • 3




    $begingroup$
    @user10915156 Well, if the creator of this world is a god then those terms suddenly mean natural phenomenon again! Amazing how that terminology problem got solved.
    $endgroup$
    – Samuel
    Apr 28 at 20:26







  • 4




    $begingroup$
    No intention of taking away from this answer, but in thinking about providing a similar answer I realized the precession of a geostationary orbit would render the position not fixed. The largest factor here would be a slow cycling of the inclination of the orbit (satellites use thrusters to counter this effect). You do note that the stability depends on the planetary system so the answer still works on shorter timescales but for long term stability a planet with less J2 (equatorial bulge) than Earth would help reduce the precession and keep the effect stable for longer.
    $endgroup$
    – ben
    Apr 28 at 20:40






  • 3




    $begingroup$
    @ben It's entirely possible that the planet in question has no precession. I was thinking about a way for the orbital mechanics to work such that solar pressure/off-gassing corrected the orbit, but that's unlikely to add much more time without violating the other precepts of the question.
    $endgroup$
    – Samuel
    Apr 28 at 20:42







  • 5




    $begingroup$
    @ben: Would the planet's own equatorial bulge make a geostationary satellite precess? By symmetry that ought to be unlikely. What nudges Earth's geostationary orbits out of the equatorial plane must be the righting moment of solar/lunar tides, causing gyroscopic precession -- but since the planet is not Earth, we can posit that it has negligible axial tilt and do away with the moon. Then a geostationary orbit should be stable, right?
    $endgroup$
    – Henning Makholm
    Apr 29 at 21:56


















39
















$begingroup$

You didn't say how far up in the sky you need your object and what type of object you want, so I suggest the plume of a volcano.



Some volcanos and geysers are quite regular in their eruptions. Your volcano will erupt not long after midnight every 24 hours and emit only a short burst of gaseous matter and fine dust-like particles that will drift upward in the still air and remain visible for 18 hours, until the evening wind scatters the cloud and it disappears.



If the eruption is just a short puff, the plume will be a small near-spherical cloud, as this one over Popocatepetl:



enter image description here



Etna even does smoke rings:



enter image description here






share|improve this answer












$endgroup$














  • $begingroup$
    pretty clever answer!
    $endgroup$
    – Fattie
    May 1 at 12:44


















17
















$begingroup$

A geostationary satellite follows an orbit which keeps it over the same point on the Earth.



https://www.skyandtelescope.com/observing/how-to-see-and-photograph-geosynchronous-satellites/



satellites



The streaks are stars which are elongated by the rotation of the earth and the long exposure. The satellites are rotating with the earth and so they look like dots. I was surprised that the satellites this blogger photographed did not track out an analemma like the sun, but he says they stay put.




Unlike the ISS and the many objects in low Earth object, geostationary
satellites are visible all night long every night of the year.




Satellites are technological objects but a thing can be in orbit and not be technological.



If something were bright and in orbit you might be able to see it all the time. You could have it get bright alternately. With satellites these are called satellite flares.



https://en.wikipedia.org/wiki/Satellite_flare




Satellite flare, also known as satellite glint, is the visible
phenomenon caused by the reflective surfaces of passing satellites
(such as antennas, SAR or solar panels), reflecting sunlight toward
the Earth below and appearing as a brief, bright "flare".




The satellites that are famous for this apparently rotate so as to present their reflective surfaces. Something in orbit could be slowly rotating, and when the non reflective side was presented it would seem to disappear to the viewer on the ground.






share|improve this answer










$endgroup$










  • 3




    $begingroup$
    Great minds... But you did include a picture, so I suspect you'll be the winner by votes.
    $endgroup$
    – Samuel
    Apr 28 at 20:16






  • 3




    $begingroup$
    @user10915156 Our satellites are technological, but a satellite does not have to be technological. It can show up and get caught by a planets gravity.
    $endgroup$
    – Willk
    Apr 28 at 22:54






  • 2




    $begingroup$
    Also it is worth pointing out that the term satellite just seems to mean something orbiting. The moon is considered a satellite.
    $endgroup$
    – Captain Man
    Apr 29 at 14:36


















14
















$begingroup$

The Sun of a tidally locked planet, eclipsed by its Moon.



Your people live on a tidally locked planet. The Sun is always in the same spot in the sky.



(Traditionally such planets' habitable zones form a ring with the Sun near the horizon, for practical reasons)



Six hours per day, the Moon passes over, eclipsing it.



Caveats:



  • The eclips's start and end are not instantaneous


  • The satellite would have to be huge and/or very close for a 25% cover. You'd have to crunch the numbers to see if the system is feasible gravitationally.






share|improve this answer










$endgroup$














  • $begingroup$
    I couldn't find a reference for the habitable ring concept, probably because I'm missing the standard term for it. If anyone knows, please do edit in a link.
    $endgroup$
    – Emilio M Bumachar
    Apr 29 at 7:39






  • 2




    $begingroup$
    If you don't want the object to be the sun, it could be a trojan asteroid at the planet's L4 or L5 point if the planet is tidally locked to the sun. The asteroid could be eclipsed, or have a variable visibility due to its own rotation and shape / albedo.
    $endgroup$
    – patstew
    Apr 29 at 11:04







  • 2




    $begingroup$
    Not possible. In order to get 25% coverage from a contact binary, you'd need the moon to be about 40% bigger than the planet; if you want a stable situation, you'd need to be further away (and have a bigger "moon"). In such a situation, the planet would tidally lock to the "moon", not the Sun.
    $endgroup$
    – Mark
    Apr 29 at 20:58



















7
















$begingroup$

This is the equation you are looking for:



$$T^2GM=4𝜋^2R^3$$



This is Kepler's third law, and it correlates mass, semi-major axis length and orbital period.



For a geostationary orbit, you have a circle with a radius of approximatelly 40,000 km. Notice, however, that what the law actually states is that:




The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.




Starting from a perfect circular orbit, you can make it elliptical. As long as you keep a semi major axis as long as the radius of a geostationary orbit, your satellite's orbital period will be 24h - but it will have a periapsis much closer to Earth, and an apoapsis much farther. It will look like this:



Elliptical orbit



Bodies always spend more time closer to the apoapsis than closer to the periapsis. That's because their orbital speed is at its maximum at the periapsis and at its lowest in the apoapsis.



Just fine tune the eccentricity of the satellite to spend a quarter of its time closer to tje Earth on the day side and you're all set.






share|improve this answer












$endgroup$














  • $begingroup$
    Could you explain how this fulfills the most important criteria, "18 hours of constant position in the sky"?
    $endgroup$
    – pipe
    Apr 29 at 7:39










  • $begingroup$
    @pipe by having a 24h orbital period, it will stay pretyy much in the same position. It will move back and forth a little, but not more than a few degrees. That's how a lot of communication satellites work.
    $endgroup$
    – Renan
    Apr 29 at 9:49










  • $begingroup$
    You need to have a circular, or very- near-circular orbit to stay within a few degrees of geostationary (and near-equatorial on top of that). The more elliptical the orbit, the lower your angular velocity near apoapsis, and the higher your angular velocity near periapsis. See Kepler's Second Law.
    $endgroup$
    – notovny
    Apr 29 at 10:13







  • 2




    $begingroup$
    @Renan If you play KSP, you can see how much Ike moves around over a Dunar day, and its orbital eccentricity is only 0.03. The issue with an elliptical synchronous orbit is that the planet rotates with a constant angular velocity, but an elliptical orbit does not, so an object that's in a synchronous orbit but not a near-circular, near-equatorial orbit will change its sky position noticeably in a repeating 24-hour pattern. celestrak.com/columns/v04n07
    $endgroup$
    – notovny
    Apr 29 at 11:43






  • 3




    $begingroup$
    If you want the position to be "effectively constant" for 18 hours, your eccentricity needs to be so high you're passing through the planet at periapsis.
    $endgroup$
    – Mark
    Apr 29 at 21:02


















5
















$begingroup$

The Coandă effect (Wiki)



It's the effect that allows a ping-pong ball to float in a hair dryer. The air clings to the rounded surface of the ball and air pressure magic keeps it in the jet, while the force of the jet itself keeps the ball afloat.



Replace the ball with a sufficiently shaped object (a smooth rock or something) and the hair dryer with a gaseous vent of sufficient strength and you can plausibly get yourself a rock floating (mostly) stationary in the sky for as long as the vent spews. If you want the rock to be higher in the sky, you can put the whole construct on top of a hill and view it from the foot of the hill or some distance away.






share|improve this answer










$endgroup$










  • 1




    $begingroup$
    I wonder if topologically speaking a tidally locked planet could take a continuous solar flare and cause this effect...without rendering the entire planet a blasted wasteland (and/or pushing it out of the solar system)
    $endgroup$
    – Ruadhan
    Apr 29 at 15:09


















4
















$begingroup$

While geostationary satellites are the ideal, and obviously-correct answer if orbital altitude is permissible, they don't work so well in higher latitudes.



For these there's a less-stationary but still viable option: a highly elliptical inclined orbit such as a Molniya Orbit or Tundra Orbit, which are designed to give a high dwell time over the area of interest.



This will appear to trace a "γ" gamma-shape in the air, slowing down to essentially stationary and then reversing in the loop:



enter image description here



It spends 2/3 of its time in the small eye of that tail - for the geostationary Tundra orbit, that's the 18 hours you asked for.



With two or more satellites following this same orbit (a "constellation"), you get essentially constant coverage.



If, because of angling of solar panels or something, the satellites are only visible at certain times, such as at the apogee (the very tip of the gamma tail) they can then essentially look like a single stationary object, that periodically blinks out briefly and then turns back on (slightly to one side of where it turned off, but you'd have to be very accurately monitoring it to notice that).



The requested gap of a few hours could either be due to a gap in the constellation, or because to be visible they require the sun to be shining on them, and they are in the earth's shadow at that time.



However, for these to be non-technological would be a stretch. A highly elliptical orbit is feasible though unlikely for a single object, but multiple objects in a constellation, not so much. So, the tricks to make it seem extremely stationary won't work.



Against the sun or stars, though, a single object in a Tundra orbit would appear essentially stationary, rising, hanging there, and setting at the same horizontal position.



Without solar panels, it'd need to be very high albedo - clean white or perhaps crystal?






share|improve this answer












$endgroup$










  • 1




    $begingroup$
    In many ways this is the best answer.
    $endgroup$
    – Fattie
    May 1 at 12:46


















3
















$begingroup$

The planet of a tidally locked satellite.



Your people live in a satellite tidally locked to a gas giant, around a red dwarf.



Similar to, and inspired by (hover to show spoiler)




https://en.wikipedia.org/wiki/Nemesis_(Asimov_novel)




The gas giant looms huge and fixed in the sky. It completely eclipses the star for six hours a day, the "day" being a revolution of the satellite around the gas giant. Having no inner light, it disappears to the naked eye while not illuminated by the star.



When the satellite is between the planet and the star, the planet is still illuminated, as the satellite is too tiny to eclipse anything.






share|improve this answer










$endgroup$














  • $begingroup$
    pretty clever, Emilio !
    $endgroup$
    – Fattie
    May 1 at 12:46


















3
















$begingroup$

Polaris already does this, at certain places on the Earth and at certain times of the year.



The title asks for an object while the body asks for a [sic] 'phenomena'; to lean towards the latter we might also entertain:



A rainbow -- you might need to fiddle with the atmosphere a bit, but I think this could be arranged; I might guess something like this already occurs on Earth near waterfalls or that sort of thing.



The auroras -- by which I mean the aurora borealis and the aurora australis -- it seems likely to me that you could fiddle enough with a planet, its magnetic field, and its sun to make these visible 18 hours a day, at least on some parts of the planet. They do tend to take up quite a large segment of the sky.






share|improve this answer










$endgroup$














  • $begingroup$
    Okay, well, good job on not being an object, I guess. But you need Hard Science evidence to back up such things lasting 18 hours, cyclic, in a human-hospitable atmosphere.
    $endgroup$
    – Malady
    Apr 29 at 23:55


















3
















$begingroup$

Lenticular wave clouds stay in place, relative to the mountain, ridge or other topographic feature that creates them, and they can persist as long as the conditions are favorable. On Earth, around the summer solstice at the right latitude (e.g. London, 51.5 degrees North), you can have around 18 hours of combined daylight and civil twilight for almost a month (depending on how precise it needs to be -- note that the length of daylight does not change rapidly from day to day around the solstices), so the visibility requirement seems feasible. You could even posit a diurnal weather pattern in which, for example, the wind dies down overnight, causing the cloud to dissipate, only to re-form as the wind picks up in the morning. With this approach, you can separate the duration issue from the hours of daylight, if you assume the cloud is visible against the stars, or your planet has sufficient moons (or bright enough stars, in a globular cluster or near a galaxy's center) that it is never fully dark at night.



Continuing with the meteorological theme, consider also the Catatumbo lightning - towering clouds by day, lit up by lightning at night, confined to a specific and relatively small geographic area, and on a diurnal cycle. From the Wikipedia article:




Italian geographer Agustin Codazzi described it: "like a continuous
lightning, and its position such that, located almost on the meridian
of the mouth of the lake, it directs the navigators as a lighthouse."




Lenticular clouds, unfortunately (for your purpose), are not likely to generate lightning, but maybe it's not too much of a stretch...






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$endgroup$






















    2
















    $begingroup$

    Make Mars go a little faster. Instead of ever seeming to move retrograde for a few months, it just seems to stop for about a day. Decrease their orbital periods and it happens as often as you want.






    share|improve this answer










    $endgroup$










    • 2




      $begingroup$
      In order for this to work, Earth's orbital period needs to be about a day, with Mars's period being only slightly longer. That close to the Sun, planets tend to evaporate.
      $endgroup$
      – Mark
      Apr 29 at 21:05


















    1
















    $begingroup$

    I can imagine a hot-air balloon type creature (similar to what Sagan imagined a living creature on Jupiter might look) that sits up however high you want in the atmosphere but periodically comes down to feed or rest (maybe it feeds on microbes high up in the atmosphere or has ultra stable DNA which allows it to live in higher radiation environments). If you're worried about it blowing around, just make it have an adaptation where it can track itself relative to the ground and is territorial.






    share|improve this answer










    $endgroup$






















      1
















      $begingroup$

      Since all the other answers are super-large scale, let's go with something a little smaller (as the question doesn't state that the same object must be visible at all places on the planet or even region).



      Birds and Heat Vents



      Imagine you have a bird (-like) creature, which can fly for extended periods of time, and is pretty communal. These birds have a very long range, but nest in large groups. Specifically, they've learned to build their nesting colonies around natural hot air vents (whether these are caused by volcanic activity, burning seams of coal, gigantic sleeping creatures, whatever). For a significant portion of the day, a constant column of these birds can be seen rising on the thermals produced by the vent at the center of their colony.



      After rising on this natural vent (lots of free altitude), they break off formation, gliding away and using their keen eyesight to catch some prey before diving for dinner. They may bring some food back if you want, or something else that causes them to stay in packs (maybe they're pack hunters, something raven-sized that eats adult deer, and carry that back to the nest).



      The constant column of birds leaving the nest from before dawn until after dusk would be a fixed sight, they'll always need to eat, and it even opens up some interesting plot (the bird column isn't out today?!?!?).






      share|improve this answer










      $endgroup$
















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        13 Answers
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        active

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        13 Answers
        13






        active

        oldest

        votes









        active

        oldest

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        active

        oldest

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        55
















        $begingroup$

        It's physically possible.



        Put a spherical object in a geostationary orbit, make it rotate about its own axis at a rate suited to your own visibility/non-visibility requirements, and make a portion of it have very low albedo.



        Staying at a single point in the sky, the object will only be visible while the higher albedo portion is facing the planet and become invisible while the low albedo portion rotates into view.



        It could technically happen by chance but would only be stable for as long as the orbit is stable, which really depends on your planetary system.






        share|improve this answer










        $endgroup$










        • 4




          $begingroup$
          Difficult to imagine another possible answer. +1
          $endgroup$
          – 011358 smell
          Apr 28 at 20:16






        • 3




          $begingroup$
          @user10915156 Well, if the creator of this world is a god then those terms suddenly mean natural phenomenon again! Amazing how that terminology problem got solved.
          $endgroup$
          – Samuel
          Apr 28 at 20:26







        • 4




          $begingroup$
          No intention of taking away from this answer, but in thinking about providing a similar answer I realized the precession of a geostationary orbit would render the position not fixed. The largest factor here would be a slow cycling of the inclination of the orbit (satellites use thrusters to counter this effect). You do note that the stability depends on the planetary system so the answer still works on shorter timescales but for long term stability a planet with less J2 (equatorial bulge) than Earth would help reduce the precession and keep the effect stable for longer.
          $endgroup$
          – ben
          Apr 28 at 20:40






        • 3




          $begingroup$
          @ben It's entirely possible that the planet in question has no precession. I was thinking about a way for the orbital mechanics to work such that solar pressure/off-gassing corrected the orbit, but that's unlikely to add much more time without violating the other precepts of the question.
          $endgroup$
          – Samuel
          Apr 28 at 20:42







        • 5




          $begingroup$
          @ben: Would the planet's own equatorial bulge make a geostationary satellite precess? By symmetry that ought to be unlikely. What nudges Earth's geostationary orbits out of the equatorial plane must be the righting moment of solar/lunar tides, causing gyroscopic precession -- but since the planet is not Earth, we can posit that it has negligible axial tilt and do away with the moon. Then a geostationary orbit should be stable, right?
          $endgroup$
          – Henning Makholm
          Apr 29 at 21:56















        55
















        $begingroup$

        It's physically possible.



        Put a spherical object in a geostationary orbit, make it rotate about its own axis at a rate suited to your own visibility/non-visibility requirements, and make a portion of it have very low albedo.



        Staying at a single point in the sky, the object will only be visible while the higher albedo portion is facing the planet and become invisible while the low albedo portion rotates into view.



        It could technically happen by chance but would only be stable for as long as the orbit is stable, which really depends on your planetary system.






        share|improve this answer










        $endgroup$










        • 4




          $begingroup$
          Difficult to imagine another possible answer. +1
          $endgroup$
          – 011358 smell
          Apr 28 at 20:16






        • 3




          $begingroup$
          @user10915156 Well, if the creator of this world is a god then those terms suddenly mean natural phenomenon again! Amazing how that terminology problem got solved.
          $endgroup$
          – Samuel
          Apr 28 at 20:26







        • 4




          $begingroup$
          No intention of taking away from this answer, but in thinking about providing a similar answer I realized the precession of a geostationary orbit would render the position not fixed. The largest factor here would be a slow cycling of the inclination of the orbit (satellites use thrusters to counter this effect). You do note that the stability depends on the planetary system so the answer still works on shorter timescales but for long term stability a planet with less J2 (equatorial bulge) than Earth would help reduce the precession and keep the effect stable for longer.
          $endgroup$
          – ben
          Apr 28 at 20:40






        • 3




          $begingroup$
          @ben It's entirely possible that the planet in question has no precession. I was thinking about a way for the orbital mechanics to work such that solar pressure/off-gassing corrected the orbit, but that's unlikely to add much more time without violating the other precepts of the question.
          $endgroup$
          – Samuel
          Apr 28 at 20:42







        • 5




          $begingroup$
          @ben: Would the planet's own equatorial bulge make a geostationary satellite precess? By symmetry that ought to be unlikely. What nudges Earth's geostationary orbits out of the equatorial plane must be the righting moment of solar/lunar tides, causing gyroscopic precession -- but since the planet is not Earth, we can posit that it has negligible axial tilt and do away with the moon. Then a geostationary orbit should be stable, right?
          $endgroup$
          – Henning Makholm
          Apr 29 at 21:56













        55














        55










        55







        $begingroup$

        It's physically possible.



        Put a spherical object in a geostationary orbit, make it rotate about its own axis at a rate suited to your own visibility/non-visibility requirements, and make a portion of it have very low albedo.



        Staying at a single point in the sky, the object will only be visible while the higher albedo portion is facing the planet and become invisible while the low albedo portion rotates into view.



        It could technically happen by chance but would only be stable for as long as the orbit is stable, which really depends on your planetary system.






        share|improve this answer










        $endgroup$



        It's physically possible.



        Put a spherical object in a geostationary orbit, make it rotate about its own axis at a rate suited to your own visibility/non-visibility requirements, and make a portion of it have very low albedo.



        Staying at a single point in the sky, the object will only be visible while the higher albedo portion is facing the planet and become invisible while the low albedo portion rotates into view.



        It could technically happen by chance but would only be stable for as long as the orbit is stable, which really depends on your planetary system.







        share|improve this answer













        share|improve this answer




        share|improve this answer



        share|improve this answer










        answered Apr 28 at 20:12









        SamuelSamuel

        45.6k8 gold badges129 silver badges222 bronze badges




        45.6k8 gold badges129 silver badges222 bronze badges










        • 4




          $begingroup$
          Difficult to imagine another possible answer. +1
          $endgroup$
          – 011358 smell
          Apr 28 at 20:16






        • 3




          $begingroup$
          @user10915156 Well, if the creator of this world is a god then those terms suddenly mean natural phenomenon again! Amazing how that terminology problem got solved.
          $endgroup$
          – Samuel
          Apr 28 at 20:26







        • 4




          $begingroup$
          No intention of taking away from this answer, but in thinking about providing a similar answer I realized the precession of a geostationary orbit would render the position not fixed. The largest factor here would be a slow cycling of the inclination of the orbit (satellites use thrusters to counter this effect). You do note that the stability depends on the planetary system so the answer still works on shorter timescales but for long term stability a planet with less J2 (equatorial bulge) than Earth would help reduce the precession and keep the effect stable for longer.
          $endgroup$
          – ben
          Apr 28 at 20:40






        • 3




          $begingroup$
          @ben It's entirely possible that the planet in question has no precession. I was thinking about a way for the orbital mechanics to work such that solar pressure/off-gassing corrected the orbit, but that's unlikely to add much more time without violating the other precepts of the question.
          $endgroup$
          – Samuel
          Apr 28 at 20:42







        • 5




          $begingroup$
          @ben: Would the planet's own equatorial bulge make a geostationary satellite precess? By symmetry that ought to be unlikely. What nudges Earth's geostationary orbits out of the equatorial plane must be the righting moment of solar/lunar tides, causing gyroscopic precession -- but since the planet is not Earth, we can posit that it has negligible axial tilt and do away with the moon. Then a geostationary orbit should be stable, right?
          $endgroup$
          – Henning Makholm
          Apr 29 at 21:56












        • 4




          $begingroup$
          Difficult to imagine another possible answer. +1
          $endgroup$
          – 011358 smell
          Apr 28 at 20:16






        • 3




          $begingroup$
          @user10915156 Well, if the creator of this world is a god then those terms suddenly mean natural phenomenon again! Amazing how that terminology problem got solved.
          $endgroup$
          – Samuel
          Apr 28 at 20:26







        • 4




          $begingroup$
          No intention of taking away from this answer, but in thinking about providing a similar answer I realized the precession of a geostationary orbit would render the position not fixed. The largest factor here would be a slow cycling of the inclination of the orbit (satellites use thrusters to counter this effect). You do note that the stability depends on the planetary system so the answer still works on shorter timescales but for long term stability a planet with less J2 (equatorial bulge) than Earth would help reduce the precession and keep the effect stable for longer.
          $endgroup$
          – ben
          Apr 28 at 20:40






        • 3




          $begingroup$
          @ben It's entirely possible that the planet in question has no precession. I was thinking about a way for the orbital mechanics to work such that solar pressure/off-gassing corrected the orbit, but that's unlikely to add much more time without violating the other precepts of the question.
          $endgroup$
          – Samuel
          Apr 28 at 20:42







        • 5




          $begingroup$
          @ben: Would the planet's own equatorial bulge make a geostationary satellite precess? By symmetry that ought to be unlikely. What nudges Earth's geostationary orbits out of the equatorial plane must be the righting moment of solar/lunar tides, causing gyroscopic precession -- but since the planet is not Earth, we can posit that it has negligible axial tilt and do away with the moon. Then a geostationary orbit should be stable, right?
          $endgroup$
          – Henning Makholm
          Apr 29 at 21:56







        4




        4




        $begingroup$
        Difficult to imagine another possible answer. +1
        $endgroup$
        – 011358 smell
        Apr 28 at 20:16




        $begingroup$
        Difficult to imagine another possible answer. +1
        $endgroup$
        – 011358 smell
        Apr 28 at 20:16




        3




        3




        $begingroup$
        @user10915156 Well, if the creator of this world is a god then those terms suddenly mean natural phenomenon again! Amazing how that terminology problem got solved.
        $endgroup$
        – Samuel
        Apr 28 at 20:26





        $begingroup$
        @user10915156 Well, if the creator of this world is a god then those terms suddenly mean natural phenomenon again! Amazing how that terminology problem got solved.
        $endgroup$
        – Samuel
        Apr 28 at 20:26





        4




        4




        $begingroup$
        No intention of taking away from this answer, but in thinking about providing a similar answer I realized the precession of a geostationary orbit would render the position not fixed. The largest factor here would be a slow cycling of the inclination of the orbit (satellites use thrusters to counter this effect). You do note that the stability depends on the planetary system so the answer still works on shorter timescales but for long term stability a planet with less J2 (equatorial bulge) than Earth would help reduce the precession and keep the effect stable for longer.
        $endgroup$
        – ben
        Apr 28 at 20:40




        $begingroup$
        No intention of taking away from this answer, but in thinking about providing a similar answer I realized the precession of a geostationary orbit would render the position not fixed. The largest factor here would be a slow cycling of the inclination of the orbit (satellites use thrusters to counter this effect). You do note that the stability depends on the planetary system so the answer still works on shorter timescales but for long term stability a planet with less J2 (equatorial bulge) than Earth would help reduce the precession and keep the effect stable for longer.
        $endgroup$
        – ben
        Apr 28 at 20:40




        3




        3




        $begingroup$
        @ben It's entirely possible that the planet in question has no precession. I was thinking about a way for the orbital mechanics to work such that solar pressure/off-gassing corrected the orbit, but that's unlikely to add much more time without violating the other precepts of the question.
        $endgroup$
        – Samuel
        Apr 28 at 20:42





        $begingroup$
        @ben It's entirely possible that the planet in question has no precession. I was thinking about a way for the orbital mechanics to work such that solar pressure/off-gassing corrected the orbit, but that's unlikely to add much more time without violating the other precepts of the question.
        $endgroup$
        – Samuel
        Apr 28 at 20:42





        5




        5




        $begingroup$
        @ben: Would the planet's own equatorial bulge make a geostationary satellite precess? By symmetry that ought to be unlikely. What nudges Earth's geostationary orbits out of the equatorial plane must be the righting moment of solar/lunar tides, causing gyroscopic precession -- but since the planet is not Earth, we can posit that it has negligible axial tilt and do away with the moon. Then a geostationary orbit should be stable, right?
        $endgroup$
        – Henning Makholm
        Apr 29 at 21:56




        $begingroup$
        @ben: Would the planet's own equatorial bulge make a geostationary satellite precess? By symmetry that ought to be unlikely. What nudges Earth's geostationary orbits out of the equatorial plane must be the righting moment of solar/lunar tides, causing gyroscopic precession -- but since the planet is not Earth, we can posit that it has negligible axial tilt and do away with the moon. Then a geostationary orbit should be stable, right?
        $endgroup$
        – Henning Makholm
        Apr 29 at 21:56













        39
















        $begingroup$

        You didn't say how far up in the sky you need your object and what type of object you want, so I suggest the plume of a volcano.



        Some volcanos and geysers are quite regular in their eruptions. Your volcano will erupt not long after midnight every 24 hours and emit only a short burst of gaseous matter and fine dust-like particles that will drift upward in the still air and remain visible for 18 hours, until the evening wind scatters the cloud and it disappears.



        If the eruption is just a short puff, the plume will be a small near-spherical cloud, as this one over Popocatepetl:



        enter image description here



        Etna even does smoke rings:



        enter image description here






        share|improve this answer












        $endgroup$














        • $begingroup$
          pretty clever answer!
          $endgroup$
          – Fattie
          May 1 at 12:44















        39
















        $begingroup$

        You didn't say how far up in the sky you need your object and what type of object you want, so I suggest the plume of a volcano.



        Some volcanos and geysers are quite regular in their eruptions. Your volcano will erupt not long after midnight every 24 hours and emit only a short burst of gaseous matter and fine dust-like particles that will drift upward in the still air and remain visible for 18 hours, until the evening wind scatters the cloud and it disappears.



        If the eruption is just a short puff, the plume will be a small near-spherical cloud, as this one over Popocatepetl:



        enter image description here



        Etna even does smoke rings:



        enter image description here






        share|improve this answer












        $endgroup$














        • $begingroup$
          pretty clever answer!
          $endgroup$
          – Fattie
          May 1 at 12:44













        39














        39










        39







        $begingroup$

        You didn't say how far up in the sky you need your object and what type of object you want, so I suggest the plume of a volcano.



        Some volcanos and geysers are quite regular in their eruptions. Your volcano will erupt not long after midnight every 24 hours and emit only a short burst of gaseous matter and fine dust-like particles that will drift upward in the still air and remain visible for 18 hours, until the evening wind scatters the cloud and it disappears.



        If the eruption is just a short puff, the plume will be a small near-spherical cloud, as this one over Popocatepetl:



        enter image description here



        Etna even does smoke rings:



        enter image description here






        share|improve this answer












        $endgroup$



        You didn't say how far up in the sky you need your object and what type of object you want, so I suggest the plume of a volcano.



        Some volcanos and geysers are quite regular in their eruptions. Your volcano will erupt not long after midnight every 24 hours and emit only a short burst of gaseous matter and fine dust-like particles that will drift upward in the still air and remain visible for 18 hours, until the evening wind scatters the cloud and it disappears.



        If the eruption is just a short puff, the plume will be a small near-spherical cloud, as this one over Popocatepetl:



        enter image description here



        Etna even does smoke rings:



        enter image description here







        share|improve this answer















        share|improve this answer




        share|improve this answer



        share|improve this answer








        edited Apr 28 at 20:45

























        answered Apr 28 at 20:35







        user64555





















        • $begingroup$
          pretty clever answer!
          $endgroup$
          – Fattie
          May 1 at 12:44
















        • $begingroup$
          pretty clever answer!
          $endgroup$
          – Fattie
          May 1 at 12:44















        $begingroup$
        pretty clever answer!
        $endgroup$
        – Fattie
        May 1 at 12:44




        $begingroup$
        pretty clever answer!
        $endgroup$
        – Fattie
        May 1 at 12:44











        17
















        $begingroup$

        A geostationary satellite follows an orbit which keeps it over the same point on the Earth.



        https://www.skyandtelescope.com/observing/how-to-see-and-photograph-geosynchronous-satellites/



        satellites



        The streaks are stars which are elongated by the rotation of the earth and the long exposure. The satellites are rotating with the earth and so they look like dots. I was surprised that the satellites this blogger photographed did not track out an analemma like the sun, but he says they stay put.




        Unlike the ISS and the many objects in low Earth object, geostationary
        satellites are visible all night long every night of the year.




        Satellites are technological objects but a thing can be in orbit and not be technological.



        If something were bright and in orbit you might be able to see it all the time. You could have it get bright alternately. With satellites these are called satellite flares.



        https://en.wikipedia.org/wiki/Satellite_flare




        Satellite flare, also known as satellite glint, is the visible
        phenomenon caused by the reflective surfaces of passing satellites
        (such as antennas, SAR or solar panels), reflecting sunlight toward
        the Earth below and appearing as a brief, bright "flare".




        The satellites that are famous for this apparently rotate so as to present their reflective surfaces. Something in orbit could be slowly rotating, and when the non reflective side was presented it would seem to disappear to the viewer on the ground.






        share|improve this answer










        $endgroup$










        • 3




          $begingroup$
          Great minds... But you did include a picture, so I suspect you'll be the winner by votes.
          $endgroup$
          – Samuel
          Apr 28 at 20:16






        • 3




          $begingroup$
          @user10915156 Our satellites are technological, but a satellite does not have to be technological. It can show up and get caught by a planets gravity.
          $endgroup$
          – Willk
          Apr 28 at 22:54






        • 2




          $begingroup$
          Also it is worth pointing out that the term satellite just seems to mean something orbiting. The moon is considered a satellite.
          $endgroup$
          – Captain Man
          Apr 29 at 14:36















        17
















        $begingroup$

        A geostationary satellite follows an orbit which keeps it over the same point on the Earth.



        https://www.skyandtelescope.com/observing/how-to-see-and-photograph-geosynchronous-satellites/



        satellites



        The streaks are stars which are elongated by the rotation of the earth and the long exposure. The satellites are rotating with the earth and so they look like dots. I was surprised that the satellites this blogger photographed did not track out an analemma like the sun, but he says they stay put.




        Unlike the ISS and the many objects in low Earth object, geostationary
        satellites are visible all night long every night of the year.




        Satellites are technological objects but a thing can be in orbit and not be technological.



        If something were bright and in orbit you might be able to see it all the time. You could have it get bright alternately. With satellites these are called satellite flares.



        https://en.wikipedia.org/wiki/Satellite_flare




        Satellite flare, also known as satellite glint, is the visible
        phenomenon caused by the reflective surfaces of passing satellites
        (such as antennas, SAR or solar panels), reflecting sunlight toward
        the Earth below and appearing as a brief, bright "flare".




        The satellites that are famous for this apparently rotate so as to present their reflective surfaces. Something in orbit could be slowly rotating, and when the non reflective side was presented it would seem to disappear to the viewer on the ground.






        share|improve this answer










        $endgroup$










        • 3




          $begingroup$
          Great minds... But you did include a picture, so I suspect you'll be the winner by votes.
          $endgroup$
          – Samuel
          Apr 28 at 20:16






        • 3




          $begingroup$
          @user10915156 Our satellites are technological, but a satellite does not have to be technological. It can show up and get caught by a planets gravity.
          $endgroup$
          – Willk
          Apr 28 at 22:54






        • 2




          $begingroup$
          Also it is worth pointing out that the term satellite just seems to mean something orbiting. The moon is considered a satellite.
          $endgroup$
          – Captain Man
          Apr 29 at 14:36













        17














        17










        17







        $begingroup$

        A geostationary satellite follows an orbit which keeps it over the same point on the Earth.



        https://www.skyandtelescope.com/observing/how-to-see-and-photograph-geosynchronous-satellites/



        satellites



        The streaks are stars which are elongated by the rotation of the earth and the long exposure. The satellites are rotating with the earth and so they look like dots. I was surprised that the satellites this blogger photographed did not track out an analemma like the sun, but he says they stay put.




        Unlike the ISS and the many objects in low Earth object, geostationary
        satellites are visible all night long every night of the year.




        Satellites are technological objects but a thing can be in orbit and not be technological.



        If something were bright and in orbit you might be able to see it all the time. You could have it get bright alternately. With satellites these are called satellite flares.



        https://en.wikipedia.org/wiki/Satellite_flare




        Satellite flare, also known as satellite glint, is the visible
        phenomenon caused by the reflective surfaces of passing satellites
        (such as antennas, SAR or solar panels), reflecting sunlight toward
        the Earth below and appearing as a brief, bright "flare".




        The satellites that are famous for this apparently rotate so as to present their reflective surfaces. Something in orbit could be slowly rotating, and when the non reflective side was presented it would seem to disappear to the viewer on the ground.






        share|improve this answer










        $endgroup$



        A geostationary satellite follows an orbit which keeps it over the same point on the Earth.



        https://www.skyandtelescope.com/observing/how-to-see-and-photograph-geosynchronous-satellites/



        satellites



        The streaks are stars which are elongated by the rotation of the earth and the long exposure. The satellites are rotating with the earth and so they look like dots. I was surprised that the satellites this blogger photographed did not track out an analemma like the sun, but he says they stay put.




        Unlike the ISS and the many objects in low Earth object, geostationary
        satellites are visible all night long every night of the year.




        Satellites are technological objects but a thing can be in orbit and not be technological.



        If something were bright and in orbit you might be able to see it all the time. You could have it get bright alternately. With satellites these are called satellite flares.



        https://en.wikipedia.org/wiki/Satellite_flare




        Satellite flare, also known as satellite glint, is the visible
        phenomenon caused by the reflective surfaces of passing satellites
        (such as antennas, SAR or solar panels), reflecting sunlight toward
        the Earth below and appearing as a brief, bright "flare".




        The satellites that are famous for this apparently rotate so as to present their reflective surfaces. Something in orbit could be slowly rotating, and when the non reflective side was presented it would seem to disappear to the viewer on the ground.







        share|improve this answer













        share|improve this answer




        share|improve this answer



        share|improve this answer










        answered Apr 28 at 20:14









        WillkWillk

        141k34 gold badges263 silver badges583 bronze badges




        141k34 gold badges263 silver badges583 bronze badges










        • 3




          $begingroup$
          Great minds... But you did include a picture, so I suspect you'll be the winner by votes.
          $endgroup$
          – Samuel
          Apr 28 at 20:16






        • 3




          $begingroup$
          @user10915156 Our satellites are technological, but a satellite does not have to be technological. It can show up and get caught by a planets gravity.
          $endgroup$
          – Willk
          Apr 28 at 22:54






        • 2




          $begingroup$
          Also it is worth pointing out that the term satellite just seems to mean something orbiting. The moon is considered a satellite.
          $endgroup$
          – Captain Man
          Apr 29 at 14:36












        • 3




          $begingroup$
          Great minds... But you did include a picture, so I suspect you'll be the winner by votes.
          $endgroup$
          – Samuel
          Apr 28 at 20:16






        • 3




          $begingroup$
          @user10915156 Our satellites are technological, but a satellite does not have to be technological. It can show up and get caught by a planets gravity.
          $endgroup$
          – Willk
          Apr 28 at 22:54






        • 2




          $begingroup$
          Also it is worth pointing out that the term satellite just seems to mean something orbiting. The moon is considered a satellite.
          $endgroup$
          – Captain Man
          Apr 29 at 14:36







        3




        3




        $begingroup$
        Great minds... But you did include a picture, so I suspect you'll be the winner by votes.
        $endgroup$
        – Samuel
        Apr 28 at 20:16




        $begingroup$
        Great minds... But you did include a picture, so I suspect you'll be the winner by votes.
        $endgroup$
        – Samuel
        Apr 28 at 20:16




        3




        3




        $begingroup$
        @user10915156 Our satellites are technological, but a satellite does not have to be technological. It can show up and get caught by a planets gravity.
        $endgroup$
        – Willk
        Apr 28 at 22:54




        $begingroup$
        @user10915156 Our satellites are technological, but a satellite does not have to be technological. It can show up and get caught by a planets gravity.
        $endgroup$
        – Willk
        Apr 28 at 22:54




        2




        2




        $begingroup$
        Also it is worth pointing out that the term satellite just seems to mean something orbiting. The moon is considered a satellite.
        $endgroup$
        – Captain Man
        Apr 29 at 14:36




        $begingroup$
        Also it is worth pointing out that the term satellite just seems to mean something orbiting. The moon is considered a satellite.
        $endgroup$
        – Captain Man
        Apr 29 at 14:36











        14
















        $begingroup$

        The Sun of a tidally locked planet, eclipsed by its Moon.



        Your people live on a tidally locked planet. The Sun is always in the same spot in the sky.



        (Traditionally such planets' habitable zones form a ring with the Sun near the horizon, for practical reasons)



        Six hours per day, the Moon passes over, eclipsing it.



        Caveats:



        • The eclips's start and end are not instantaneous


        • The satellite would have to be huge and/or very close for a 25% cover. You'd have to crunch the numbers to see if the system is feasible gravitationally.






        share|improve this answer










        $endgroup$














        • $begingroup$
          I couldn't find a reference for the habitable ring concept, probably because I'm missing the standard term for it. If anyone knows, please do edit in a link.
          $endgroup$
          – Emilio M Bumachar
          Apr 29 at 7:39






        • 2




          $begingroup$
          If you don't want the object to be the sun, it could be a trojan asteroid at the planet's L4 or L5 point if the planet is tidally locked to the sun. The asteroid could be eclipsed, or have a variable visibility due to its own rotation and shape / albedo.
          $endgroup$
          – patstew
          Apr 29 at 11:04







        • 2




          $begingroup$
          Not possible. In order to get 25% coverage from a contact binary, you'd need the moon to be about 40% bigger than the planet; if you want a stable situation, you'd need to be further away (and have a bigger "moon"). In such a situation, the planet would tidally lock to the "moon", not the Sun.
          $endgroup$
          – Mark
          Apr 29 at 20:58
















        14
















        $begingroup$

        The Sun of a tidally locked planet, eclipsed by its Moon.



        Your people live on a tidally locked planet. The Sun is always in the same spot in the sky.



        (Traditionally such planets' habitable zones form a ring with the Sun near the horizon, for practical reasons)



        Six hours per day, the Moon passes over, eclipsing it.



        Caveats:



        • The eclips's start and end are not instantaneous


        • The satellite would have to be huge and/or very close for a 25% cover. You'd have to crunch the numbers to see if the system is feasible gravitationally.






        share|improve this answer










        $endgroup$














        • $begingroup$
          I couldn't find a reference for the habitable ring concept, probably because I'm missing the standard term for it. If anyone knows, please do edit in a link.
          $endgroup$
          – Emilio M Bumachar
          Apr 29 at 7:39






        • 2




          $begingroup$
          If you don't want the object to be the sun, it could be a trojan asteroid at the planet's L4 or L5 point if the planet is tidally locked to the sun. The asteroid could be eclipsed, or have a variable visibility due to its own rotation and shape / albedo.
          $endgroup$
          – patstew
          Apr 29 at 11:04







        • 2




          $begingroup$
          Not possible. In order to get 25% coverage from a contact binary, you'd need the moon to be about 40% bigger than the planet; if you want a stable situation, you'd need to be further away (and have a bigger "moon"). In such a situation, the planet would tidally lock to the "moon", not the Sun.
          $endgroup$
          – Mark
          Apr 29 at 20:58














        14














        14










        14







        $begingroup$

        The Sun of a tidally locked planet, eclipsed by its Moon.



        Your people live on a tidally locked planet. The Sun is always in the same spot in the sky.



        (Traditionally such planets' habitable zones form a ring with the Sun near the horizon, for practical reasons)



        Six hours per day, the Moon passes over, eclipsing it.



        Caveats:



        • The eclips's start and end are not instantaneous


        • The satellite would have to be huge and/or very close for a 25% cover. You'd have to crunch the numbers to see if the system is feasible gravitationally.






        share|improve this answer










        $endgroup$



        The Sun of a tidally locked planet, eclipsed by its Moon.



        Your people live on a tidally locked planet. The Sun is always in the same spot in the sky.



        (Traditionally such planets' habitable zones form a ring with the Sun near the horizon, for practical reasons)



        Six hours per day, the Moon passes over, eclipsing it.



        Caveats:



        • The eclips's start and end are not instantaneous


        • The satellite would have to be huge and/or very close for a 25% cover. You'd have to crunch the numbers to see if the system is feasible gravitationally.







        share|improve this answer













        share|improve this answer




        share|improve this answer



        share|improve this answer










        answered Apr 29 at 7:38









        Emilio M BumacharEmilio M Bumachar

        5,18112 silver badges25 bronze badges




        5,18112 silver badges25 bronze badges














        • $begingroup$
          I couldn't find a reference for the habitable ring concept, probably because I'm missing the standard term for it. If anyone knows, please do edit in a link.
          $endgroup$
          – Emilio M Bumachar
          Apr 29 at 7:39






        • 2




          $begingroup$
          If you don't want the object to be the sun, it could be a trojan asteroid at the planet's L4 or L5 point if the planet is tidally locked to the sun. The asteroid could be eclipsed, or have a variable visibility due to its own rotation and shape / albedo.
          $endgroup$
          – patstew
          Apr 29 at 11:04







        • 2




          $begingroup$
          Not possible. In order to get 25% coverage from a contact binary, you'd need the moon to be about 40% bigger than the planet; if you want a stable situation, you'd need to be further away (and have a bigger "moon"). In such a situation, the planet would tidally lock to the "moon", not the Sun.
          $endgroup$
          – Mark
          Apr 29 at 20:58

















        • $begingroup$
          I couldn't find a reference for the habitable ring concept, probably because I'm missing the standard term for it. If anyone knows, please do edit in a link.
          $endgroup$
          – Emilio M Bumachar
          Apr 29 at 7:39






        • 2




          $begingroup$
          If you don't want the object to be the sun, it could be a trojan asteroid at the planet's L4 or L5 point if the planet is tidally locked to the sun. The asteroid could be eclipsed, or have a variable visibility due to its own rotation and shape / albedo.
          $endgroup$
          – patstew
          Apr 29 at 11:04







        • 2




          $begingroup$
          Not possible. In order to get 25% coverage from a contact binary, you'd need the moon to be about 40% bigger than the planet; if you want a stable situation, you'd need to be further away (and have a bigger "moon"). In such a situation, the planet would tidally lock to the "moon", not the Sun.
          $endgroup$
          – Mark
          Apr 29 at 20:58
















        $begingroup$
        I couldn't find a reference for the habitable ring concept, probably because I'm missing the standard term for it. If anyone knows, please do edit in a link.
        $endgroup$
        – Emilio M Bumachar
        Apr 29 at 7:39




        $begingroup$
        I couldn't find a reference for the habitable ring concept, probably because I'm missing the standard term for it. If anyone knows, please do edit in a link.
        $endgroup$
        – Emilio M Bumachar
        Apr 29 at 7:39




        2




        2




        $begingroup$
        If you don't want the object to be the sun, it could be a trojan asteroid at the planet's L4 or L5 point if the planet is tidally locked to the sun. The asteroid could be eclipsed, or have a variable visibility due to its own rotation and shape / albedo.
        $endgroup$
        – patstew
        Apr 29 at 11:04





        $begingroup$
        If you don't want the object to be the sun, it could be a trojan asteroid at the planet's L4 or L5 point if the planet is tidally locked to the sun. The asteroid could be eclipsed, or have a variable visibility due to its own rotation and shape / albedo.
        $endgroup$
        – patstew
        Apr 29 at 11:04





        2




        2




        $begingroup$
        Not possible. In order to get 25% coverage from a contact binary, you'd need the moon to be about 40% bigger than the planet; if you want a stable situation, you'd need to be further away (and have a bigger "moon"). In such a situation, the planet would tidally lock to the "moon", not the Sun.
        $endgroup$
        – Mark
        Apr 29 at 20:58





        $begingroup$
        Not possible. In order to get 25% coverage from a contact binary, you'd need the moon to be about 40% bigger than the planet; if you want a stable situation, you'd need to be further away (and have a bigger "moon"). In such a situation, the planet would tidally lock to the "moon", not the Sun.
        $endgroup$
        – Mark
        Apr 29 at 20:58












        7
















        $begingroup$

        This is the equation you are looking for:



        $$T^2GM=4𝜋^2R^3$$



        This is Kepler's third law, and it correlates mass, semi-major axis length and orbital period.



        For a geostationary orbit, you have a circle with a radius of approximatelly 40,000 km. Notice, however, that what the law actually states is that:




        The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.




        Starting from a perfect circular orbit, you can make it elliptical. As long as you keep a semi major axis as long as the radius of a geostationary orbit, your satellite's orbital period will be 24h - but it will have a periapsis much closer to Earth, and an apoapsis much farther. It will look like this:



        Elliptical orbit



        Bodies always spend more time closer to the apoapsis than closer to the periapsis. That's because their orbital speed is at its maximum at the periapsis and at its lowest in the apoapsis.



        Just fine tune the eccentricity of the satellite to spend a quarter of its time closer to tje Earth on the day side and you're all set.






        share|improve this answer












        $endgroup$














        • $begingroup$
          Could you explain how this fulfills the most important criteria, "18 hours of constant position in the sky"?
          $endgroup$
          – pipe
          Apr 29 at 7:39










        • $begingroup$
          @pipe by having a 24h orbital period, it will stay pretyy much in the same position. It will move back and forth a little, but not more than a few degrees. That's how a lot of communication satellites work.
          $endgroup$
          – Renan
          Apr 29 at 9:49










        • $begingroup$
          You need to have a circular, or very- near-circular orbit to stay within a few degrees of geostationary (and near-equatorial on top of that). The more elliptical the orbit, the lower your angular velocity near apoapsis, and the higher your angular velocity near periapsis. See Kepler's Second Law.
          $endgroup$
          – notovny
          Apr 29 at 10:13







        • 2




          $begingroup$
          @Renan If you play KSP, you can see how much Ike moves around over a Dunar day, and its orbital eccentricity is only 0.03. The issue with an elliptical synchronous orbit is that the planet rotates with a constant angular velocity, but an elliptical orbit does not, so an object that's in a synchronous orbit but not a near-circular, near-equatorial orbit will change its sky position noticeably in a repeating 24-hour pattern. celestrak.com/columns/v04n07
          $endgroup$
          – notovny
          Apr 29 at 11:43






        • 3




          $begingroup$
          If you want the position to be "effectively constant" for 18 hours, your eccentricity needs to be so high you're passing through the planet at periapsis.
          $endgroup$
          – Mark
          Apr 29 at 21:02















        7
















        $begingroup$

        This is the equation you are looking for:



        $$T^2GM=4𝜋^2R^3$$



        This is Kepler's third law, and it correlates mass, semi-major axis length and orbital period.



        For a geostationary orbit, you have a circle with a radius of approximatelly 40,000 km. Notice, however, that what the law actually states is that:




        The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.




        Starting from a perfect circular orbit, you can make it elliptical. As long as you keep a semi major axis as long as the radius of a geostationary orbit, your satellite's orbital period will be 24h - but it will have a periapsis much closer to Earth, and an apoapsis much farther. It will look like this:



        Elliptical orbit



        Bodies always spend more time closer to the apoapsis than closer to the periapsis. That's because their orbital speed is at its maximum at the periapsis and at its lowest in the apoapsis.



        Just fine tune the eccentricity of the satellite to spend a quarter of its time closer to tje Earth on the day side and you're all set.






        share|improve this answer












        $endgroup$














        • $begingroup$
          Could you explain how this fulfills the most important criteria, "18 hours of constant position in the sky"?
          $endgroup$
          – pipe
          Apr 29 at 7:39










        • $begingroup$
          @pipe by having a 24h orbital period, it will stay pretyy much in the same position. It will move back and forth a little, but not more than a few degrees. That's how a lot of communication satellites work.
          $endgroup$
          – Renan
          Apr 29 at 9:49










        • $begingroup$
          You need to have a circular, or very- near-circular orbit to stay within a few degrees of geostationary (and near-equatorial on top of that). The more elliptical the orbit, the lower your angular velocity near apoapsis, and the higher your angular velocity near periapsis. See Kepler's Second Law.
          $endgroup$
          – notovny
          Apr 29 at 10:13







        • 2




          $begingroup$
          @Renan If you play KSP, you can see how much Ike moves around over a Dunar day, and its orbital eccentricity is only 0.03. The issue with an elliptical synchronous orbit is that the planet rotates with a constant angular velocity, but an elliptical orbit does not, so an object that's in a synchronous orbit but not a near-circular, near-equatorial orbit will change its sky position noticeably in a repeating 24-hour pattern. celestrak.com/columns/v04n07
          $endgroup$
          – notovny
          Apr 29 at 11:43






        • 3




          $begingroup$
          If you want the position to be "effectively constant" for 18 hours, your eccentricity needs to be so high you're passing through the planet at periapsis.
          $endgroup$
          – Mark
          Apr 29 at 21:02













        7














        7










        7







        $begingroup$

        This is the equation you are looking for:



        $$T^2GM=4𝜋^2R^3$$



        This is Kepler's third law, and it correlates mass, semi-major axis length and orbital period.



        For a geostationary orbit, you have a circle with a radius of approximatelly 40,000 km. Notice, however, that what the law actually states is that:




        The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.




        Starting from a perfect circular orbit, you can make it elliptical. As long as you keep a semi major axis as long as the radius of a geostationary orbit, your satellite's orbital period will be 24h - but it will have a periapsis much closer to Earth, and an apoapsis much farther. It will look like this:



        Elliptical orbit



        Bodies always spend more time closer to the apoapsis than closer to the periapsis. That's because their orbital speed is at its maximum at the periapsis and at its lowest in the apoapsis.



        Just fine tune the eccentricity of the satellite to spend a quarter of its time closer to tje Earth on the day side and you're all set.






        share|improve this answer












        $endgroup$



        This is the equation you are looking for:



        $$T^2GM=4𝜋^2R^3$$



        This is Kepler's third law, and it correlates mass, semi-major axis length and orbital period.



        For a geostationary orbit, you have a circle with a radius of approximatelly 40,000 km. Notice, however, that what the law actually states is that:




        The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.




        Starting from a perfect circular orbit, you can make it elliptical. As long as you keep a semi major axis as long as the radius of a geostationary orbit, your satellite's orbital period will be 24h - but it will have a periapsis much closer to Earth, and an apoapsis much farther. It will look like this:



        Elliptical orbit



        Bodies always spend more time closer to the apoapsis than closer to the periapsis. That's because their orbital speed is at its maximum at the periapsis and at its lowest in the apoapsis.



        Just fine tune the eccentricity of the satellite to spend a quarter of its time closer to tje Earth on the day side and you're all set.







        share|improve this answer















        share|improve this answer




        share|improve this answer



        share|improve this answer








        edited Apr 29 at 7:02

























        answered Apr 29 at 5:15









        RenanRenan

        70.2k21 gold badges158 silver badges339 bronze badges




        70.2k21 gold badges158 silver badges339 bronze badges














        • $begingroup$
          Could you explain how this fulfills the most important criteria, "18 hours of constant position in the sky"?
          $endgroup$
          – pipe
          Apr 29 at 7:39










        • $begingroup$
          @pipe by having a 24h orbital period, it will stay pretyy much in the same position. It will move back and forth a little, but not more than a few degrees. That's how a lot of communication satellites work.
          $endgroup$
          – Renan
          Apr 29 at 9:49










        • $begingroup$
          You need to have a circular, or very- near-circular orbit to stay within a few degrees of geostationary (and near-equatorial on top of that). The more elliptical the orbit, the lower your angular velocity near apoapsis, and the higher your angular velocity near periapsis. See Kepler's Second Law.
          $endgroup$
          – notovny
          Apr 29 at 10:13







        • 2




          $begingroup$
          @Renan If you play KSP, you can see how much Ike moves around over a Dunar day, and its orbital eccentricity is only 0.03. The issue with an elliptical synchronous orbit is that the planet rotates with a constant angular velocity, but an elliptical orbit does not, so an object that's in a synchronous orbit but not a near-circular, near-equatorial orbit will change its sky position noticeably in a repeating 24-hour pattern. celestrak.com/columns/v04n07
          $endgroup$
          – notovny
          Apr 29 at 11:43






        • 3




          $begingroup$
          If you want the position to be "effectively constant" for 18 hours, your eccentricity needs to be so high you're passing through the planet at periapsis.
          $endgroup$
          – Mark
          Apr 29 at 21:02
















        • $begingroup$
          Could you explain how this fulfills the most important criteria, "18 hours of constant position in the sky"?
          $endgroup$
          – pipe
          Apr 29 at 7:39










        • $begingroup$
          @pipe by having a 24h orbital period, it will stay pretyy much in the same position. It will move back and forth a little, but not more than a few degrees. That's how a lot of communication satellites work.
          $endgroup$
          – Renan
          Apr 29 at 9:49










        • $begingroup$
          You need to have a circular, or very- near-circular orbit to stay within a few degrees of geostationary (and near-equatorial on top of that). The more elliptical the orbit, the lower your angular velocity near apoapsis, and the higher your angular velocity near periapsis. See Kepler's Second Law.
          $endgroup$
          – notovny
          Apr 29 at 10:13







        • 2




          $begingroup$
          @Renan If you play KSP, you can see how much Ike moves around over a Dunar day, and its orbital eccentricity is only 0.03. The issue with an elliptical synchronous orbit is that the planet rotates with a constant angular velocity, but an elliptical orbit does not, so an object that's in a synchronous orbit but not a near-circular, near-equatorial orbit will change its sky position noticeably in a repeating 24-hour pattern. celestrak.com/columns/v04n07
          $endgroup$
          – notovny
          Apr 29 at 11:43






        • 3




          $begingroup$
          If you want the position to be "effectively constant" for 18 hours, your eccentricity needs to be so high you're passing through the planet at periapsis.
          $endgroup$
          – Mark
          Apr 29 at 21:02















        $begingroup$
        Could you explain how this fulfills the most important criteria, "18 hours of constant position in the sky"?
        $endgroup$
        – pipe
        Apr 29 at 7:39




        $begingroup$
        Could you explain how this fulfills the most important criteria, "18 hours of constant position in the sky"?
        $endgroup$
        – pipe
        Apr 29 at 7:39












        $begingroup$
        @pipe by having a 24h orbital period, it will stay pretyy much in the same position. It will move back and forth a little, but not more than a few degrees. That's how a lot of communication satellites work.
        $endgroup$
        – Renan
        Apr 29 at 9:49




        $begingroup$
        @pipe by having a 24h orbital period, it will stay pretyy much in the same position. It will move back and forth a little, but not more than a few degrees. That's how a lot of communication satellites work.
        $endgroup$
        – Renan
        Apr 29 at 9:49












        $begingroup$
        You need to have a circular, or very- near-circular orbit to stay within a few degrees of geostationary (and near-equatorial on top of that). The more elliptical the orbit, the lower your angular velocity near apoapsis, and the higher your angular velocity near periapsis. See Kepler's Second Law.
        $endgroup$
        – notovny
        Apr 29 at 10:13





        $begingroup$
        You need to have a circular, or very- near-circular orbit to stay within a few degrees of geostationary (and near-equatorial on top of that). The more elliptical the orbit, the lower your angular velocity near apoapsis, and the higher your angular velocity near periapsis. See Kepler's Second Law.
        $endgroup$
        – notovny
        Apr 29 at 10:13





        2




        2




        $begingroup$
        @Renan If you play KSP, you can see how much Ike moves around over a Dunar day, and its orbital eccentricity is only 0.03. The issue with an elliptical synchronous orbit is that the planet rotates with a constant angular velocity, but an elliptical orbit does not, so an object that's in a synchronous orbit but not a near-circular, near-equatorial orbit will change its sky position noticeably in a repeating 24-hour pattern. celestrak.com/columns/v04n07
        $endgroup$
        – notovny
        Apr 29 at 11:43




        $begingroup$
        @Renan If you play KSP, you can see how much Ike moves around over a Dunar day, and its orbital eccentricity is only 0.03. The issue with an elliptical synchronous orbit is that the planet rotates with a constant angular velocity, but an elliptical orbit does not, so an object that's in a synchronous orbit but not a near-circular, near-equatorial orbit will change its sky position noticeably in a repeating 24-hour pattern. celestrak.com/columns/v04n07
        $endgroup$
        – notovny
        Apr 29 at 11:43




        3




        3




        $begingroup$
        If you want the position to be "effectively constant" for 18 hours, your eccentricity needs to be so high you're passing through the planet at periapsis.
        $endgroup$
        – Mark
        Apr 29 at 21:02




        $begingroup$
        If you want the position to be "effectively constant" for 18 hours, your eccentricity needs to be so high you're passing through the planet at periapsis.
        $endgroup$
        – Mark
        Apr 29 at 21:02











        5
















        $begingroup$

        The Coandă effect (Wiki)



        It's the effect that allows a ping-pong ball to float in a hair dryer. The air clings to the rounded surface of the ball and air pressure magic keeps it in the jet, while the force of the jet itself keeps the ball afloat.



        Replace the ball with a sufficiently shaped object (a smooth rock or something) and the hair dryer with a gaseous vent of sufficient strength and you can plausibly get yourself a rock floating (mostly) stationary in the sky for as long as the vent spews. If you want the rock to be higher in the sky, you can put the whole construct on top of a hill and view it from the foot of the hill or some distance away.






        share|improve this answer










        $endgroup$










        • 1




          $begingroup$
          I wonder if topologically speaking a tidally locked planet could take a continuous solar flare and cause this effect...without rendering the entire planet a blasted wasteland (and/or pushing it out of the solar system)
          $endgroup$
          – Ruadhan
          Apr 29 at 15:09















        5
















        $begingroup$

        The Coandă effect (Wiki)



        It's the effect that allows a ping-pong ball to float in a hair dryer. The air clings to the rounded surface of the ball and air pressure magic keeps it in the jet, while the force of the jet itself keeps the ball afloat.



        Replace the ball with a sufficiently shaped object (a smooth rock or something) and the hair dryer with a gaseous vent of sufficient strength and you can plausibly get yourself a rock floating (mostly) stationary in the sky for as long as the vent spews. If you want the rock to be higher in the sky, you can put the whole construct on top of a hill and view it from the foot of the hill or some distance away.






        share|improve this answer










        $endgroup$










        • 1




          $begingroup$
          I wonder if topologically speaking a tidally locked planet could take a continuous solar flare and cause this effect...without rendering the entire planet a blasted wasteland (and/or pushing it out of the solar system)
          $endgroup$
          – Ruadhan
          Apr 29 at 15:09













        5














        5










        5







        $begingroup$

        The Coandă effect (Wiki)



        It's the effect that allows a ping-pong ball to float in a hair dryer. The air clings to the rounded surface of the ball and air pressure magic keeps it in the jet, while the force of the jet itself keeps the ball afloat.



        Replace the ball with a sufficiently shaped object (a smooth rock or something) and the hair dryer with a gaseous vent of sufficient strength and you can plausibly get yourself a rock floating (mostly) stationary in the sky for as long as the vent spews. If you want the rock to be higher in the sky, you can put the whole construct on top of a hill and view it from the foot of the hill or some distance away.






        share|improve this answer










        $endgroup$



        The Coandă effect (Wiki)



        It's the effect that allows a ping-pong ball to float in a hair dryer. The air clings to the rounded surface of the ball and air pressure magic keeps it in the jet, while the force of the jet itself keeps the ball afloat.



        Replace the ball with a sufficiently shaped object (a smooth rock or something) and the hair dryer with a gaseous vent of sufficient strength and you can plausibly get yourself a rock floating (mostly) stationary in the sky for as long as the vent spews. If you want the rock to be higher in the sky, you can put the whole construct on top of a hill and view it from the foot of the hill or some distance away.







        share|improve this answer













        share|improve this answer




        share|improve this answer



        share|improve this answer










        answered Apr 29 at 13:07









        SuthekSuthek

        1513 bronze badges




        1513 bronze badges










        • 1




          $begingroup$
          I wonder if topologically speaking a tidally locked planet could take a continuous solar flare and cause this effect...without rendering the entire planet a blasted wasteland (and/or pushing it out of the solar system)
          $endgroup$
          – Ruadhan
          Apr 29 at 15:09












        • 1




          $begingroup$
          I wonder if topologically speaking a tidally locked planet could take a continuous solar flare and cause this effect...without rendering the entire planet a blasted wasteland (and/or pushing it out of the solar system)
          $endgroup$
          – Ruadhan
          Apr 29 at 15:09







        1




        1




        $begingroup$
        I wonder if topologically speaking a tidally locked planet could take a continuous solar flare and cause this effect...without rendering the entire planet a blasted wasteland (and/or pushing it out of the solar system)
        $endgroup$
        – Ruadhan
        Apr 29 at 15:09




        $begingroup$
        I wonder if topologically speaking a tidally locked planet could take a continuous solar flare and cause this effect...without rendering the entire planet a blasted wasteland (and/or pushing it out of the solar system)
        $endgroup$
        – Ruadhan
        Apr 29 at 15:09











        4
















        $begingroup$

        While geostationary satellites are the ideal, and obviously-correct answer if orbital altitude is permissible, they don't work so well in higher latitudes.



        For these there's a less-stationary but still viable option: a highly elliptical inclined orbit such as a Molniya Orbit or Tundra Orbit, which are designed to give a high dwell time over the area of interest.



        This will appear to trace a "γ" gamma-shape in the air, slowing down to essentially stationary and then reversing in the loop:



        enter image description here



        It spends 2/3 of its time in the small eye of that tail - for the geostationary Tundra orbit, that's the 18 hours you asked for.



        With two or more satellites following this same orbit (a "constellation"), you get essentially constant coverage.



        If, because of angling of solar panels or something, the satellites are only visible at certain times, such as at the apogee (the very tip of the gamma tail) they can then essentially look like a single stationary object, that periodically blinks out briefly and then turns back on (slightly to one side of where it turned off, but you'd have to be very accurately monitoring it to notice that).



        The requested gap of a few hours could either be due to a gap in the constellation, or because to be visible they require the sun to be shining on them, and they are in the earth's shadow at that time.



        However, for these to be non-technological would be a stretch. A highly elliptical orbit is feasible though unlikely for a single object, but multiple objects in a constellation, not so much. So, the tricks to make it seem extremely stationary won't work.



        Against the sun or stars, though, a single object in a Tundra orbit would appear essentially stationary, rising, hanging there, and setting at the same horizontal position.



        Without solar panels, it'd need to be very high albedo - clean white or perhaps crystal?






        share|improve this answer












        $endgroup$










        • 1




          $begingroup$
          In many ways this is the best answer.
          $endgroup$
          – Fattie
          May 1 at 12:46















        4
















        $begingroup$

        While geostationary satellites are the ideal, and obviously-correct answer if orbital altitude is permissible, they don't work so well in higher latitudes.



        For these there's a less-stationary but still viable option: a highly elliptical inclined orbit such as a Molniya Orbit or Tundra Orbit, which are designed to give a high dwell time over the area of interest.



        This will appear to trace a "γ" gamma-shape in the air, slowing down to essentially stationary and then reversing in the loop:



        enter image description here



        It spends 2/3 of its time in the small eye of that tail - for the geostationary Tundra orbit, that's the 18 hours you asked for.



        With two or more satellites following this same orbit (a "constellation"), you get essentially constant coverage.



        If, because of angling of solar panels or something, the satellites are only visible at certain times, such as at the apogee (the very tip of the gamma tail) they can then essentially look like a single stationary object, that periodically blinks out briefly and then turns back on (slightly to one side of where it turned off, but you'd have to be very accurately monitoring it to notice that).



        The requested gap of a few hours could either be due to a gap in the constellation, or because to be visible they require the sun to be shining on them, and they are in the earth's shadow at that time.



        However, for these to be non-technological would be a stretch. A highly elliptical orbit is feasible though unlikely for a single object, but multiple objects in a constellation, not so much. So, the tricks to make it seem extremely stationary won't work.



        Against the sun or stars, though, a single object in a Tundra orbit would appear essentially stationary, rising, hanging there, and setting at the same horizontal position.



        Without solar panels, it'd need to be very high albedo - clean white or perhaps crystal?






        share|improve this answer












        $endgroup$










        • 1




          $begingroup$
          In many ways this is the best answer.
          $endgroup$
          – Fattie
          May 1 at 12:46













        4














        4










        4







        $begingroup$

        While geostationary satellites are the ideal, and obviously-correct answer if orbital altitude is permissible, they don't work so well in higher latitudes.



        For these there's a less-stationary but still viable option: a highly elliptical inclined orbit such as a Molniya Orbit or Tundra Orbit, which are designed to give a high dwell time over the area of interest.



        This will appear to trace a "γ" gamma-shape in the air, slowing down to essentially stationary and then reversing in the loop:



        enter image description here



        It spends 2/3 of its time in the small eye of that tail - for the geostationary Tundra orbit, that's the 18 hours you asked for.



        With two or more satellites following this same orbit (a "constellation"), you get essentially constant coverage.



        If, because of angling of solar panels or something, the satellites are only visible at certain times, such as at the apogee (the very tip of the gamma tail) they can then essentially look like a single stationary object, that periodically blinks out briefly and then turns back on (slightly to one side of where it turned off, but you'd have to be very accurately monitoring it to notice that).



        The requested gap of a few hours could either be due to a gap in the constellation, or because to be visible they require the sun to be shining on them, and they are in the earth's shadow at that time.



        However, for these to be non-technological would be a stretch. A highly elliptical orbit is feasible though unlikely for a single object, but multiple objects in a constellation, not so much. So, the tricks to make it seem extremely stationary won't work.



        Against the sun or stars, though, a single object in a Tundra orbit would appear essentially stationary, rising, hanging there, and setting at the same horizontal position.



        Without solar panels, it'd need to be very high albedo - clean white or perhaps crystal?






        share|improve this answer












        $endgroup$



        While geostationary satellites are the ideal, and obviously-correct answer if orbital altitude is permissible, they don't work so well in higher latitudes.



        For these there's a less-stationary but still viable option: a highly elliptical inclined orbit such as a Molniya Orbit or Tundra Orbit, which are designed to give a high dwell time over the area of interest.



        This will appear to trace a "γ" gamma-shape in the air, slowing down to essentially stationary and then reversing in the loop:



        enter image description here



        It spends 2/3 of its time in the small eye of that tail - for the geostationary Tundra orbit, that's the 18 hours you asked for.



        With two or more satellites following this same orbit (a "constellation"), you get essentially constant coverage.



        If, because of angling of solar panels or something, the satellites are only visible at certain times, such as at the apogee (the very tip of the gamma tail) they can then essentially look like a single stationary object, that periodically blinks out briefly and then turns back on (slightly to one side of where it turned off, but you'd have to be very accurately monitoring it to notice that).



        The requested gap of a few hours could either be due to a gap in the constellation, or because to be visible they require the sun to be shining on them, and they are in the earth's shadow at that time.



        However, for these to be non-technological would be a stretch. A highly elliptical orbit is feasible though unlikely for a single object, but multiple objects in a constellation, not so much. So, the tricks to make it seem extremely stationary won't work.



        Against the sun or stars, though, a single object in a Tundra orbit would appear essentially stationary, rising, hanging there, and setting at the same horizontal position.



        Without solar panels, it'd need to be very high albedo - clean white or perhaps crystal?







        share|improve this answer















        share|improve this answer




        share|improve this answer



        share|improve this answer








        edited May 3 at 16:34

























        answered Apr 29 at 16:17









        Dewi MorganDewi Morgan

        6,44614 silver badges40 bronze badges




        6,44614 silver badges40 bronze badges










        • 1




          $begingroup$
          In many ways this is the best answer.
          $endgroup$
          – Fattie
          May 1 at 12:46












        • 1




          $begingroup$
          In many ways this is the best answer.
          $endgroup$
          – Fattie
          May 1 at 12:46







        1




        1




        $begingroup$
        In many ways this is the best answer.
        $endgroup$
        – Fattie
        May 1 at 12:46




        $begingroup$
        In many ways this is the best answer.
        $endgroup$
        – Fattie
        May 1 at 12:46











        3
















        $begingroup$

        The planet of a tidally locked satellite.



        Your people live in a satellite tidally locked to a gas giant, around a red dwarf.



        Similar to, and inspired by (hover to show spoiler)




        https://en.wikipedia.org/wiki/Nemesis_(Asimov_novel)




        The gas giant looms huge and fixed in the sky. It completely eclipses the star for six hours a day, the "day" being a revolution of the satellite around the gas giant. Having no inner light, it disappears to the naked eye while not illuminated by the star.



        When the satellite is between the planet and the star, the planet is still illuminated, as the satellite is too tiny to eclipse anything.






        share|improve this answer










        $endgroup$














        • $begingroup$
          pretty clever, Emilio !
          $endgroup$
          – Fattie
          May 1 at 12:46















        3
















        $begingroup$

        The planet of a tidally locked satellite.



        Your people live in a satellite tidally locked to a gas giant, around a red dwarf.



        Similar to, and inspired by (hover to show spoiler)




        https://en.wikipedia.org/wiki/Nemesis_(Asimov_novel)




        The gas giant looms huge and fixed in the sky. It completely eclipses the star for six hours a day, the "day" being a revolution of the satellite around the gas giant. Having no inner light, it disappears to the naked eye while not illuminated by the star.



        When the satellite is between the planet and the star, the planet is still illuminated, as the satellite is too tiny to eclipse anything.






        share|improve this answer










        $endgroup$














        • $begingroup$
          pretty clever, Emilio !
          $endgroup$
          – Fattie
          May 1 at 12:46













        3














        3










        3







        $begingroup$

        The planet of a tidally locked satellite.



        Your people live in a satellite tidally locked to a gas giant, around a red dwarf.



        Similar to, and inspired by (hover to show spoiler)




        https://en.wikipedia.org/wiki/Nemesis_(Asimov_novel)




        The gas giant looms huge and fixed in the sky. It completely eclipses the star for six hours a day, the "day" being a revolution of the satellite around the gas giant. Having no inner light, it disappears to the naked eye while not illuminated by the star.



        When the satellite is between the planet and the star, the planet is still illuminated, as the satellite is too tiny to eclipse anything.






        share|improve this answer










        $endgroup$



        The planet of a tidally locked satellite.



        Your people live in a satellite tidally locked to a gas giant, around a red dwarf.



        Similar to, and inspired by (hover to show spoiler)




        https://en.wikipedia.org/wiki/Nemesis_(Asimov_novel)




        The gas giant looms huge and fixed in the sky. It completely eclipses the star for six hours a day, the "day" being a revolution of the satellite around the gas giant. Having no inner light, it disappears to the naked eye while not illuminated by the star.



        When the satellite is between the planet and the star, the planet is still illuminated, as the satellite is too tiny to eclipse anything.







        share|improve this answer













        share|improve this answer




        share|improve this answer



        share|improve this answer










        answered Apr 29 at 8:04









        Emilio M BumacharEmilio M Bumachar

        5,18112 silver badges25 bronze badges




        5,18112 silver badges25 bronze badges














        • $begingroup$
          pretty clever, Emilio !
          $endgroup$
          – Fattie
          May 1 at 12:46
















        • $begingroup$
          pretty clever, Emilio !
          $endgroup$
          – Fattie
          May 1 at 12:46















        $begingroup$
        pretty clever, Emilio !
        $endgroup$
        – Fattie
        May 1 at 12:46




        $begingroup$
        pretty clever, Emilio !
        $endgroup$
        – Fattie
        May 1 at 12:46











        3
















        $begingroup$

        Polaris already does this, at certain places on the Earth and at certain times of the year.



        The title asks for an object while the body asks for a [sic] 'phenomena'; to lean towards the latter we might also entertain:



        A rainbow -- you might need to fiddle with the atmosphere a bit, but I think this could be arranged; I might guess something like this already occurs on Earth near waterfalls or that sort of thing.



        The auroras -- by which I mean the aurora borealis and the aurora australis -- it seems likely to me that you could fiddle enough with a planet, its magnetic field, and its sun to make these visible 18 hours a day, at least on some parts of the planet. They do tend to take up quite a large segment of the sky.






        share|improve this answer










        $endgroup$














        • $begingroup$
          Okay, well, good job on not being an object, I guess. But you need Hard Science evidence to back up such things lasting 18 hours, cyclic, in a human-hospitable atmosphere.
          $endgroup$
          – Malady
          Apr 29 at 23:55















        3
















        $begingroup$

        Polaris already does this, at certain places on the Earth and at certain times of the year.



        The title asks for an object while the body asks for a [sic] 'phenomena'; to lean towards the latter we might also entertain:



        A rainbow -- you might need to fiddle with the atmosphere a bit, but I think this could be arranged; I might guess something like this already occurs on Earth near waterfalls or that sort of thing.



        The auroras -- by which I mean the aurora borealis and the aurora australis -- it seems likely to me that you could fiddle enough with a planet, its magnetic field, and its sun to make these visible 18 hours a day, at least on some parts of the planet. They do tend to take up quite a large segment of the sky.






        share|improve this answer










        $endgroup$














        • $begingroup$
          Okay, well, good job on not being an object, I guess. But you need Hard Science evidence to back up such things lasting 18 hours, cyclic, in a human-hospitable atmosphere.
          $endgroup$
          – Malady
          Apr 29 at 23:55













        3














        3










        3







        $begingroup$

        Polaris already does this, at certain places on the Earth and at certain times of the year.



        The title asks for an object while the body asks for a [sic] 'phenomena'; to lean towards the latter we might also entertain:



        A rainbow -- you might need to fiddle with the atmosphere a bit, but I think this could be arranged; I might guess something like this already occurs on Earth near waterfalls or that sort of thing.



        The auroras -- by which I mean the aurora borealis and the aurora australis -- it seems likely to me that you could fiddle enough with a planet, its magnetic field, and its sun to make these visible 18 hours a day, at least on some parts of the planet. They do tend to take up quite a large segment of the sky.






        share|improve this answer










        $endgroup$



        Polaris already does this, at certain places on the Earth and at certain times of the year.



        The title asks for an object while the body asks for a [sic] 'phenomena'; to lean towards the latter we might also entertain:



        A rainbow -- you might need to fiddle with the atmosphere a bit, but I think this could be arranged; I might guess something like this already occurs on Earth near waterfalls or that sort of thing.



        The auroras -- by which I mean the aurora borealis and the aurora australis -- it seems likely to me that you could fiddle enough with a planet, its magnetic field, and its sun to make these visible 18 hours a day, at least on some parts of the planet. They do tend to take up quite a large segment of the sky.







        share|improve this answer













        share|improve this answer




        share|improve this answer



        share|improve this answer










        answered Apr 29 at 19:32









        RogerRoger

        3,9694 silver badges23 bronze badges




        3,9694 silver badges23 bronze badges














        • $begingroup$
          Okay, well, good job on not being an object, I guess. But you need Hard Science evidence to back up such things lasting 18 hours, cyclic, in a human-hospitable atmosphere.
          $endgroup$
          – Malady
          Apr 29 at 23:55
















        • $begingroup$
          Okay, well, good job on not being an object, I guess. But you need Hard Science evidence to back up such things lasting 18 hours, cyclic, in a human-hospitable atmosphere.
          $endgroup$
          – Malady
          Apr 29 at 23:55















        $begingroup$
        Okay, well, good job on not being an object, I guess. But you need Hard Science evidence to back up such things lasting 18 hours, cyclic, in a human-hospitable atmosphere.
        $endgroup$
        – Malady
        Apr 29 at 23:55




        $begingroup$
        Okay, well, good job on not being an object, I guess. But you need Hard Science evidence to back up such things lasting 18 hours, cyclic, in a human-hospitable atmosphere.
        $endgroup$
        – Malady
        Apr 29 at 23:55











        3
















        $begingroup$

        Lenticular wave clouds stay in place, relative to the mountain, ridge or other topographic feature that creates them, and they can persist as long as the conditions are favorable. On Earth, around the summer solstice at the right latitude (e.g. London, 51.5 degrees North), you can have around 18 hours of combined daylight and civil twilight for almost a month (depending on how precise it needs to be -- note that the length of daylight does not change rapidly from day to day around the solstices), so the visibility requirement seems feasible. You could even posit a diurnal weather pattern in which, for example, the wind dies down overnight, causing the cloud to dissipate, only to re-form as the wind picks up in the morning. With this approach, you can separate the duration issue from the hours of daylight, if you assume the cloud is visible against the stars, or your planet has sufficient moons (or bright enough stars, in a globular cluster or near a galaxy's center) that it is never fully dark at night.



        Continuing with the meteorological theme, consider also the Catatumbo lightning - towering clouds by day, lit up by lightning at night, confined to a specific and relatively small geographic area, and on a diurnal cycle. From the Wikipedia article:




        Italian geographer Agustin Codazzi described it: "like a continuous
        lightning, and its position such that, located almost on the meridian
        of the mouth of the lake, it directs the navigators as a lighthouse."




        Lenticular clouds, unfortunately (for your purpose), are not likely to generate lightning, but maybe it's not too much of a stretch...






        share|improve this answer












        $endgroup$



















          3
















          $begingroup$

          Lenticular wave clouds stay in place, relative to the mountain, ridge or other topographic feature that creates them, and they can persist as long as the conditions are favorable. On Earth, around the summer solstice at the right latitude (e.g. London, 51.5 degrees North), you can have around 18 hours of combined daylight and civil twilight for almost a month (depending on how precise it needs to be -- note that the length of daylight does not change rapidly from day to day around the solstices), so the visibility requirement seems feasible. You could even posit a diurnal weather pattern in which, for example, the wind dies down overnight, causing the cloud to dissipate, only to re-form as the wind picks up in the morning. With this approach, you can separate the duration issue from the hours of daylight, if you assume the cloud is visible against the stars, or your planet has sufficient moons (or bright enough stars, in a globular cluster or near a galaxy's center) that it is never fully dark at night.



          Continuing with the meteorological theme, consider also the Catatumbo lightning - towering clouds by day, lit up by lightning at night, confined to a specific and relatively small geographic area, and on a diurnal cycle. From the Wikipedia article:




          Italian geographer Agustin Codazzi described it: "like a continuous
          lightning, and its position such that, located almost on the meridian
          of the mouth of the lake, it directs the navigators as a lighthouse."




          Lenticular clouds, unfortunately (for your purpose), are not likely to generate lightning, but maybe it's not too much of a stretch...






          share|improve this answer












          $endgroup$

















            3














            3










            3







            $begingroup$

            Lenticular wave clouds stay in place, relative to the mountain, ridge or other topographic feature that creates them, and they can persist as long as the conditions are favorable. On Earth, around the summer solstice at the right latitude (e.g. London, 51.5 degrees North), you can have around 18 hours of combined daylight and civil twilight for almost a month (depending on how precise it needs to be -- note that the length of daylight does not change rapidly from day to day around the solstices), so the visibility requirement seems feasible. You could even posit a diurnal weather pattern in which, for example, the wind dies down overnight, causing the cloud to dissipate, only to re-form as the wind picks up in the morning. With this approach, you can separate the duration issue from the hours of daylight, if you assume the cloud is visible against the stars, or your planet has sufficient moons (or bright enough stars, in a globular cluster or near a galaxy's center) that it is never fully dark at night.



            Continuing with the meteorological theme, consider also the Catatumbo lightning - towering clouds by day, lit up by lightning at night, confined to a specific and relatively small geographic area, and on a diurnal cycle. From the Wikipedia article:




            Italian geographer Agustin Codazzi described it: "like a continuous
            lightning, and its position such that, located almost on the meridian
            of the mouth of the lake, it directs the navigators as a lighthouse."




            Lenticular clouds, unfortunately (for your purpose), are not likely to generate lightning, but maybe it's not too much of a stretch...






            share|improve this answer












            $endgroup$



            Lenticular wave clouds stay in place, relative to the mountain, ridge or other topographic feature that creates them, and they can persist as long as the conditions are favorable. On Earth, around the summer solstice at the right latitude (e.g. London, 51.5 degrees North), you can have around 18 hours of combined daylight and civil twilight for almost a month (depending on how precise it needs to be -- note that the length of daylight does not change rapidly from day to day around the solstices), so the visibility requirement seems feasible. You could even posit a diurnal weather pattern in which, for example, the wind dies down overnight, causing the cloud to dissipate, only to re-form as the wind picks up in the morning. With this approach, you can separate the duration issue from the hours of daylight, if you assume the cloud is visible against the stars, or your planet has sufficient moons (or bright enough stars, in a globular cluster or near a galaxy's center) that it is never fully dark at night.



            Continuing with the meteorological theme, consider also the Catatumbo lightning - towering clouds by day, lit up by lightning at night, confined to a specific and relatively small geographic area, and on a diurnal cycle. From the Wikipedia article:




            Italian geographer Agustin Codazzi described it: "like a continuous
            lightning, and its position such that, located almost on the meridian
            of the mouth of the lake, it directs the navigators as a lighthouse."




            Lenticular clouds, unfortunately (for your purpose), are not likely to generate lightning, but maybe it's not too much of a stretch...







            share|improve this answer















            share|improve this answer




            share|improve this answer



            share|improve this answer








            edited Aug 29 at 18:49

























            answered Apr 29 at 21:46









            sdenhamsdenham

            1313 bronze badges




            1313 bronze badges
























                2
















                $begingroup$

                Make Mars go a little faster. Instead of ever seeming to move retrograde for a few months, it just seems to stop for about a day. Decrease their orbital periods and it happens as often as you want.






                share|improve this answer










                $endgroup$










                • 2




                  $begingroup$
                  In order for this to work, Earth's orbital period needs to be about a day, with Mars's period being only slightly longer. That close to the Sun, planets tend to evaporate.
                  $endgroup$
                  – Mark
                  Apr 29 at 21:05















                2
















                $begingroup$

                Make Mars go a little faster. Instead of ever seeming to move retrograde for a few months, it just seems to stop for about a day. Decrease their orbital periods and it happens as often as you want.






                share|improve this answer










                $endgroup$










                • 2




                  $begingroup$
                  In order for this to work, Earth's orbital period needs to be about a day, with Mars's period being only slightly longer. That close to the Sun, planets tend to evaporate.
                  $endgroup$
                  – Mark
                  Apr 29 at 21:05













                2














                2










                2







                $begingroup$

                Make Mars go a little faster. Instead of ever seeming to move retrograde for a few months, it just seems to stop for about a day. Decrease their orbital periods and it happens as often as you want.






                share|improve this answer










                $endgroup$



                Make Mars go a little faster. Instead of ever seeming to move retrograde for a few months, it just seems to stop for about a day. Decrease their orbital periods and it happens as often as you want.







                share|improve this answer













                share|improve this answer




                share|improve this answer



                share|improve this answer










                answered Apr 28 at 22:40









                MazuraMazura

                2,9389 silver badges14 bronze badges




                2,9389 silver badges14 bronze badges










                • 2




                  $begingroup$
                  In order for this to work, Earth's orbital period needs to be about a day, with Mars's period being only slightly longer. That close to the Sun, planets tend to evaporate.
                  $endgroup$
                  – Mark
                  Apr 29 at 21:05












                • 2




                  $begingroup$
                  In order for this to work, Earth's orbital period needs to be about a day, with Mars's period being only slightly longer. That close to the Sun, planets tend to evaporate.
                  $endgroup$
                  – Mark
                  Apr 29 at 21:05







                2




                2




                $begingroup$
                In order for this to work, Earth's orbital period needs to be about a day, with Mars's period being only slightly longer. That close to the Sun, planets tend to evaporate.
                $endgroup$
                – Mark
                Apr 29 at 21:05




                $begingroup$
                In order for this to work, Earth's orbital period needs to be about a day, with Mars's period being only slightly longer. That close to the Sun, planets tend to evaporate.
                $endgroup$
                – Mark
                Apr 29 at 21:05











                1
















                $begingroup$

                I can imagine a hot-air balloon type creature (similar to what Sagan imagined a living creature on Jupiter might look) that sits up however high you want in the atmosphere but periodically comes down to feed or rest (maybe it feeds on microbes high up in the atmosphere or has ultra stable DNA which allows it to live in higher radiation environments). If you're worried about it blowing around, just make it have an adaptation where it can track itself relative to the ground and is territorial.






                share|improve this answer










                $endgroup$



















                  1
















                  $begingroup$

                  I can imagine a hot-air balloon type creature (similar to what Sagan imagined a living creature on Jupiter might look) that sits up however high you want in the atmosphere but periodically comes down to feed or rest (maybe it feeds on microbes high up in the atmosphere or has ultra stable DNA which allows it to live in higher radiation environments). If you're worried about it blowing around, just make it have an adaptation where it can track itself relative to the ground and is territorial.






                  share|improve this answer










                  $endgroup$

















                    1














                    1










                    1







                    $begingroup$

                    I can imagine a hot-air balloon type creature (similar to what Sagan imagined a living creature on Jupiter might look) that sits up however high you want in the atmosphere but periodically comes down to feed or rest (maybe it feeds on microbes high up in the atmosphere or has ultra stable DNA which allows it to live in higher radiation environments). If you're worried about it blowing around, just make it have an adaptation where it can track itself relative to the ground and is territorial.






                    share|improve this answer










                    $endgroup$



                    I can imagine a hot-air balloon type creature (similar to what Sagan imagined a living creature on Jupiter might look) that sits up however high you want in the atmosphere but periodically comes down to feed or rest (maybe it feeds on microbes high up in the atmosphere or has ultra stable DNA which allows it to live in higher radiation environments). If you're worried about it blowing around, just make it have an adaptation where it can track itself relative to the ground and is territorial.







                    share|improve this answer













                    share|improve this answer




                    share|improve this answer



                    share|improve this answer










                    answered Apr 29 at 9:04









                    spacetyperspacetyper

                    1424 bronze badges




                    1424 bronze badges
























                        1
















                        $begingroup$

                        Since all the other answers are super-large scale, let's go with something a little smaller (as the question doesn't state that the same object must be visible at all places on the planet or even region).



                        Birds and Heat Vents



                        Imagine you have a bird (-like) creature, which can fly for extended periods of time, and is pretty communal. These birds have a very long range, but nest in large groups. Specifically, they've learned to build their nesting colonies around natural hot air vents (whether these are caused by volcanic activity, burning seams of coal, gigantic sleeping creatures, whatever). For a significant portion of the day, a constant column of these birds can be seen rising on the thermals produced by the vent at the center of their colony.



                        After rising on this natural vent (lots of free altitude), they break off formation, gliding away and using their keen eyesight to catch some prey before diving for dinner. They may bring some food back if you want, or something else that causes them to stay in packs (maybe they're pack hunters, something raven-sized that eats adult deer, and carry that back to the nest).



                        The constant column of birds leaving the nest from before dawn until after dusk would be a fixed sight, they'll always need to eat, and it even opens up some interesting plot (the bird column isn't out today?!?!?).






                        share|improve this answer










                        $endgroup$



















                          1
















                          $begingroup$

                          Since all the other answers are super-large scale, let's go with something a little smaller (as the question doesn't state that the same object must be visible at all places on the planet or even region).



                          Birds and Heat Vents



                          Imagine you have a bird (-like) creature, which can fly for extended periods of time, and is pretty communal. These birds have a very long range, but nest in large groups. Specifically, they've learned to build their nesting colonies around natural hot air vents (whether these are caused by volcanic activity, burning seams of coal, gigantic sleeping creatures, whatever). For a significant portion of the day, a constant column of these birds can be seen rising on the thermals produced by the vent at the center of their colony.



                          After rising on this natural vent (lots of free altitude), they break off formation, gliding away and using their keen eyesight to catch some prey before diving for dinner. They may bring some food back if you want, or something else that causes them to stay in packs (maybe they're pack hunters, something raven-sized that eats adult deer, and carry that back to the nest).



                          The constant column of birds leaving the nest from before dawn until after dusk would be a fixed sight, they'll always need to eat, and it even opens up some interesting plot (the bird column isn't out today?!?!?).






                          share|improve this answer










                          $endgroup$

















                            1














                            1










                            1







                            $begingroup$

                            Since all the other answers are super-large scale, let's go with something a little smaller (as the question doesn't state that the same object must be visible at all places on the planet or even region).



                            Birds and Heat Vents



                            Imagine you have a bird (-like) creature, which can fly for extended periods of time, and is pretty communal. These birds have a very long range, but nest in large groups. Specifically, they've learned to build their nesting colonies around natural hot air vents (whether these are caused by volcanic activity, burning seams of coal, gigantic sleeping creatures, whatever). For a significant portion of the day, a constant column of these birds can be seen rising on the thermals produced by the vent at the center of their colony.



                            After rising on this natural vent (lots of free altitude), they break off formation, gliding away and using their keen eyesight to catch some prey before diving for dinner. They may bring some food back if you want, or something else that causes them to stay in packs (maybe they're pack hunters, something raven-sized that eats adult deer, and carry that back to the nest).



                            The constant column of birds leaving the nest from before dawn until after dusk would be a fixed sight, they'll always need to eat, and it even opens up some interesting plot (the bird column isn't out today?!?!?).






                            share|improve this answer










                            $endgroup$



                            Since all the other answers are super-large scale, let's go with something a little smaller (as the question doesn't state that the same object must be visible at all places on the planet or even region).



                            Birds and Heat Vents



                            Imagine you have a bird (-like) creature, which can fly for extended periods of time, and is pretty communal. These birds have a very long range, but nest in large groups. Specifically, they've learned to build their nesting colonies around natural hot air vents (whether these are caused by volcanic activity, burning seams of coal, gigantic sleeping creatures, whatever). For a significant portion of the day, a constant column of these birds can be seen rising on the thermals produced by the vent at the center of their colony.



                            After rising on this natural vent (lots of free altitude), they break off formation, gliding away and using their keen eyesight to catch some prey before diving for dinner. They may bring some food back if you want, or something else that causes them to stay in packs (maybe they're pack hunters, something raven-sized that eats adult deer, and carry that back to the nest).



                            The constant column of birds leaving the nest from before dawn until after dusk would be a fixed sight, they'll always need to eat, and it even opens up some interesting plot (the bird column isn't out today?!?!?).







                            share|improve this answer













                            share|improve this answer




                            share|improve this answer



                            share|improve this answer










                            answered Apr 30 at 21:45









                            DeliothDelioth

                            2932 silver badges7 bronze badges




                            2932 silver badges7 bronze badges































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