<p>I posted a few animations, just to make sure :) The image is hopefully obviously not to scale.</p>
<p>This is possible:</p>
<p><a href="https://i.sstatic.net/FXXLj.gif" rel="noreferrer"><img src="https://i.sstatic.net/FXXLj.gif" alt="Animation of a planet with rings perpendicular to its orbital plane" /></a></p>
<p>and is, in fact, not far from what Uranus is doing.</p>
<p>The animation above was produced using Mathematica. The camera is above the plane of the planet's orbit, but not directly above the star. The rings are perpendicular to the plane of the orbit. Because the camera is off-center, we see a little bit of the side of the rings. Because the camera is at a finite distance, the angle between the plane of the rings and the line of sight from the camera varies along the orbit.</p>
<p>On the other hand, the animation shown below is physically impossible. Conservation of angular momentum prohibits it:</p>
<p><a href="https://i.sstatic.net/HfVYb.gif" rel="noreferrer"><img src="https://i.sstatic.net/HfVYb.gif" alt="Animation of an impossible planet with rings always sideways to the sun" /></a></p>
<p>The ring is on the plane of the orbits of the particles the ring consists of, and (the direction of the normal of) this plane does not change during the orbit of the planet. Initially I thought that the ring would automatically be on the plane of the equator of the planet. Which is the case with Saturn's main rings and those of Uranus. However, <a href="https://astronomy.stackexchange.com/a/839/2342">as explained here</a>, there is no law of physics that would make this necessary. Even Saturn has a thin faint ring in a different orientation.</p>
<p>My limited understanding is that the origin of the ring plays a role. If a ring consists of the remains of a former satellite, then it will follow whatever orbit that satellite had. On the other hand, if the ring was formed together with the planetary system, or even ejecta from the forming planet, then it feels natural that the ring should be exactly on the equatorial plane.</p>
<p>We need an astronomer to give more details. After taking a peek at Wikipedia I suspect that a ring on the equatorial plane may be more stable. Particularly, if/when &quot;shepherd moons&quot; need to be present to keep the ring intact. Obviously the satellites tend to be near the equatorial plane of the mother planet. May be the gravity of the remaining satellites would perturb a ring in some other orientation more severely, meaning that it would not last long?</p>

CC BY-SA 4.0
2021-01-10T18:52:36.560Z
What if this planet was tidally locked to the host star?
WarpPrime
CC BY-SA 4.0
2021-01-10T19:24:18.077Z
@fasterthanlight Then the host star is on the equatorial plane of the planet, right? Implying that so are the rings (if any can survive under the circumstances). The axis of the planet is perpendicular to the plane of the ring.
Jyrki Lahtonen
CC BY-SA 4.0
2021-01-10T19:52:27.330Z
Actually I'm no longer sure about that. Anyway, the direction of the normal of the plane of the ring should be (near) constant, a tidal lock notwithstanding. So it would still be the situation in the top animation. And I think that the tidal forces of the star are strong enough to lock the planet, then they would also break apart the ring. I'm afraid I don't know.
Jyrki Lahtonen
CC BY-SA 4.0
2021-01-11T13:51:43.093Z
The second case is not as impossible as it may seem. In fact, the rings follow a Sun synchronous orbit https://en.wikipedia.org/wiki/Sun-synchronous_orbit which is a very real thing.
Pere
CC BY-SA 4.0
2021-01-11T14:58:53.190Z
Continuation of this question: https://astronomy.stackexchange.com/questions/40820/are-there-any-planetary-ring-system-other-than-phoebe-ring-not-aligned-to-the
Nilay Ghosh
CC BY-SA 4.0
2021-01-11T15:47:38.733Z
@Pere 1- The rings typically follow the equator of the planet (due to angular momentum conservation) if, as the more common case, they are formed from protoplanetary dust. The sun synchronous orbit you mentioned would be for the planet, then this means that the planet's orbit and rotation, and consequently the rings, would be in the same plane (so, all parallel). The case you mentioned, of the rings being sun synchronous, saying the second case would be possible, defy linear/angular momentum conservation. But props to Jyrki
José Andrade
CC BY-SA 4.0
2021-01-11T16:02:17.257Z
2- To understand that it is not possible (or at least, in the planetary case, nearly impossible, but possible as in a thought experiment), just see how the rings move in relation to the planet, they spin around the planet in an awkward manner. Instead of the case like Saturn, where they spin in a disk (or like a hockey puck on ice), each particle of the rings has its own orbit, and the rings spin like a spinning coin on a table with the orbit time of the ring, being the same as the planet's orbit time. That is just weird. In this case you cannot add spin like the one of Saturn's rings...3
José Andrade
CC BY-SA 4.0
2021-01-11T16:04:45.907Z
3- as doing so means you create a cloud of dust, where all the particles collide and slowly coalesce into the actual plane allowed by the angular momentum, which is nothing like the case of a star-synchronous orbit  that you described. In other words, a ring system in a star-synchronous orbit is a highly (mega hyper) unstable equilibrium point.
José Andrade
CC BY-SA 4.0
2021-01-11T16:35:41.610Z
@Pere An interesting possibility. At some point I had included a parenthetical remark *precession is possible, but we ignore that*. Then I removed it for I thought it would be confusing. Anyway, I'm not acquainted well enough with celestial mechanics to be able to tell whether a sizable ring can stably follow the kind of orbit you had in mind.
Jyrki Lahtonen
CC BY-SA 4.0
2021-01-11T22:40:23.613Z
The point being that I did not know that fast enough precession could be feasibly achieved. What was the period with the Earth's axis again? 26000 years?
Jyrki Lahtonen
CC BY-SA 4.0
2021-01-12T09:44:19.477Z
I was thinking about this again last night and noticed I made a mistake, that the parts on the rotation axis (the coin on table type) actually have no orbital speed, and would just fall onto the planet, secondly, the orbits are around the center of mass of the planet, not an axis (as in, of course you have an axis of rotation, but the projection of the rotation is on one point, not along the axis), meaning that kind of orbit is not possible
José Andrade
CC BY-SA 4.0
2021-01-12T09:54:22.250Z
regarding precession and all other effects that come from more than 2 body mechanics, I am also not versed enough into that, but for sure that angular and linear momenta would not allow the case where the rings would align with the rotating plane including the star-planet line in the perpendicular of the orbit
José Andrade
CC BY-SA 4.0
2021-01-15T05:13:59.290Z
Triton is closer to Neptune than the moon is to Earth. It orbits in the opposite direction of Neptune's spin and precesses between about 7 degrees and 53 degrees from the plane of Neptune's rotation. A Wikipedia source predicts that in less than 4 billion years Triton will be within the Roche limit an will break up to form a ring system. Therefore, Neptune will have rings that will not only be non-equatorial, but possibly still precess.
Jack R. Woods
CC BY-SA 4.0
2021-05-17T10:06:10.547Z
@Ilmari Exactly what you did to the GIFs to make them repeat indefinitely? It is a bit of a puzzle to me. Some of my old animated GIFs in Math.SE do loop infinitely, but the new ones won't. Even if I specify the parameter in Mathematica to Inifinity. I have a vague recollection that there was a SW change at some point, but I was never up to speed with that.
Jyrki Lahtonen
CC BY-SA 4.0
2021-05-17T11:16:04.803Z
@JyrkiLahtonen: GIF animations have a loop count setting; if it's 0, the animation loops forever. A lot of GIF editing software allows changing the setting; I think I used [gifsicle](http://www.lcdf.org/gifsicle/). [Here's a few other options.](https://superuser.com/questions/159212/how-do-i-make-an-existing-animated-gif-loop-repeatedly)
Ilmari Karonen
CC BY-SA 4.0
2021-05-17T12:46:17.843Z
@IlmariKaronen Apparently you managed it, but tinkering with the `AnimationRepetitions` parameter with Mathematica should do the same but won't. Irrespective of whether I set that parameter to $7$, $\infty$, or $0$. The animation is shown in browser exactly twice. This before it gets anywhere near imgur and their stuff. I thought the issue is browser related. Or a site policy even? I recall a thread where it was announced that the number of repetitiions was limited on purpose because users were abusing it. I thought you know some dirty tricks.
Jyrki Lahtonen
CC BY-SA 4.0
2021-05-17T12:48:41.920Z
FWIW Mac OS X tools are of no use to me. I'm on Windows, for better or for worse :-)
Jyrki Lahtonen
CC BY-SA 4.0
2021-05-17T13:16:34.233Z
@IlmariKaronen I learned that it is a bug in Mathematica, introduced in version 11 that I'm unlucky to own. [A fix](https://mathematica.stackexchange.com/a/238597/1155), kind of.
Jyrki Lahtonen
CC BY-SA 4.0
2021-05-17T13:29:41.827Z
@JyrkiLahtonen: Gifsicle is cross-platform. [Here's a Windows build.](https://eternallybored.org/misc/gifsicle/)
Ilmari Karonen
CC BY-SA 4.0
2021-05-17T13:30:46.640Z
Thanks @IlmariKaronen
Jyrki Lahtonen
CC BY-SA 4.0
2021-01-10T17:29:52.333Z
2021-01-11T11:40:54.830Z
2021-01-11T11:40:54.830Z
Jyrki Lahtonen
<p>Yes, the plane of the <a href="https://en.m.wikipedia.org/wiki/Rings_of_Uranus" rel="nofollow noreferrer">rings of Uranus</a> are at about 98 degrees to the plane of its orbit around the Sun.</p>
<p>This means that the ring system looks as in your picture twice per orbit. As the planet orbits the Sun, the rings, although still inclined at 98 degrees to the orbital plane gradually become &quot;face-on&quot; when viewed from the Sun. This will happen about quarter of an orbital period after the configuration illustrated in the picture. Then another quarter of an orbital period later, Uranus will be on the other side of the Sun, but with its rings tilted as shown.</p>
<p>What cannot happen is that the rings are oriented as shown throughout the entirety of a planet's orbit. Conservation of angular momentum demands that the plane of the rings (or the axis of rotation of the ring material) does not vary, unless some external torque were brought to bear in order to change it. Therefore after a quarter of an orbit, the rings in your picture would be face-on to the star.</p>

CC BY-SA 4.0
2021-01-10T10:34:57.340Z
When you say "cannot be permanently in that configuration", do you mean the orientation of the rings periodically oscillates (within one orbital cycle) or that eventually the orbit of the ring will change over many orbital cycles?
Curious Cat
CC BY-SA 4.0
2021-01-10T11:02:43.760Z
@CuriousCat The orientation of the rings in space stays the same. But the planet orbits the star. The apparent orientation of the rings with respect to the star  will therefore change from as shown in your picture, to the rings being "face-on" to the star, quarter of an orbit later.
ProfRob
CC BY-SA 4.0
2021-01-10T21:36:13.297Z
Is it possible for planetary rings to be perpendicular to their planet's axial tilt?
Mazura
CC BY-SA 4.0
2021-01-10T22:16:46.220Z
@Mazura that is a different question.
ProfRob
CC BY-SA 4.0
2021-01-10T22:21:10.593Z
Yeah but it's the fun part of this one. "the rings of Uranus are at about 98 degrees to the plane of its orbit around the Sun [because... that's exactly what its axial tilt is as it's the one planet that 'got tipped over']." As far as the rings are concerned, their sphere of influence is the planet, not the sun.
Mazura
CC BY-SA 4.0
2021-01-10T23:42:04.723Z
@Mazura and the answer is that if the rings are produced by the breakup of a captured satellite, then yes they can be. If the rings are formed at the same time as the planet, then no they can't. Some of Saturn's rings are out of the equatorial plane. None of this would change my answer.
ProfRob
CC BY-SA 4.0
2021-01-11T09:16:42.550Z
"Some of Saturn's rings are out of the equatorial plane". Are you talking about [Phoebe ring](https://en.wikipedia.org/wiki/Rings_of_Saturn#Phoebe_ring) which is tilted 27 deg  from the planet equatorial plane? On a unrelated note: Do other planets except Saturn has their rings in the same plane to the equatorial plane? I can ask a separate question if you want.
Nilay Ghosh
CC BY-SA 4.0
2021-01-10T10:26:28.983Z
2021-07-11T08:49:22.500Z
2021-07-11T08:49:22.500Z
ProfRob
<p><a href="https://i.sstatic.net/naxGH.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/naxGH.png" alt="enter image description here" /></a></p>
<p>Is it possible for planetary rings to be perpendicular (or near perpendicular) to the planet's orbit around the host star?</p>

CC BY-SA 4.0
2021-01-10T22:38:43.910Z
Why might it not be, please?
Robbie Goodwin
CC BY-SA 4.0
2021-01-11T08:42:28.113Z
Are you assuming anything about the orientation of the planet's rotational axis?
Peter Mortensen
CC BY-SA 4.0
2021-01-13T04:56:28.970Z
camera was sideways!
blankip
<exoplanet><planetary-ring>
Is it possible for planetary rings to be perpendicular (or near perpendicular) to the planet's orbit around the host star?
Curious Cat
# Is it possible for planetary rings to be perpendicular (or near perpendicular) to the planet's orbit around the host star?

(Asked by: username_0 on 2021-01-10)

[![enter image description here](https://i.sstatic.net/naxGH.png)](https://i.sstatic.net/naxGH.png)

Is it possible for planetary rings to be perpendicular (or near perpendicular) to the planet's orbit around the host star?

**Tags:** exoplanet, planetary-ring
> **Comments:**
> **username_1**: Why might it not be, please?  
> **username_2**: Are you assuming anything about the orientation of the planet's rotational axis?  
> **username_3**: camera was sideways!  

---

## 2 answers

### Answer by username_11 on 2021-01-10. Score: 50

Yes, the plane of the [rings of Uranus](https://en.m.wikipedia.org/wiki/Rings_of_Uranus) are at about 98 degrees to the plane of its orbit around the Sun.

This means that the ring system looks as in your picture twice per orbit. As the planet orbits the Sun, the rings, although still inclined at 98 degrees to the orbital plane gradually become "face-on" when viewed from the Sun. This will happen about quarter of an orbital period after the configuration illustrated in the picture. Then another quarter of an orbital period later, Uranus will be on the other side of the Sun, but with its rings tilted as shown.

What cannot happen is that the rings are oriented as shown throughout the entirety of a planet's orbit. Conservation of angular momentum demands that the plane of the rings (or the axis of rotation of the ring material) does not vary, unless some external torque were brought to bear in order to change it. Therefore after a quarter of an orbit, the rings in your picture would be face-on to the star.

> **Comments:**
> **username_0**: When you say "cannot be permanently in that configuration", do you mean the orientation of the rings periodically oscillates (within one orbital cycle) or that eventually the orbit of the ring will change over many orbital cycles?  
> **username_11**: @CuriousCat The orientation of the rings in space stays the same. But the planet orbits the star. The apparent orientation of the rings with respect to the star  will therefore change from as shown in your picture, to the rings being "face-on" to the star, quarter of an orbit later.  
> **username_12**: Is it possible for planetary rings to be perpendicular to their planet's axial tilt?  
> **username_11**: @Mazura that is a different question.  
> **username_12**: Yeah but it's the fun part of this one. "the rings of Uranus are at about 98 degrees to the plane of its orbit around the Sun [because... that's exactly what its axial tilt is as it's the one planet that 'got tipped over']." As far as the rings are concerned, their sphere of influence is the planet, not the sun.  
> **username_11**: @Mazura and the answer is that if the rings are produced by the breakup of a captured satellite, then yes they can be. If the rings are formed at the same time as the planet, then no they can't. Some of Saturn's rings are out of the equatorial plane. None of this would change my answer.  
> **username_7**: "Some of Saturn's rings are out of the equatorial plane". Are you talking about [Phoebe ring](https://en.wikipedia.org/wiki/Rings_of_Saturn#Phoebe_ring) which is tilted 27 deg  from the planet equatorial plane? On a unrelated note: Do other planets except Saturn has their rings in the same plane to the equatorial plane? I can ask a separate question if you want.  

---

### Answer by username_4 on 2021-01-10. Score: 31

I posted a few animations, just to make sure :) The image is hopefully obviously not to scale.

This is possible:

[![Animation of a planet with rings perpendicular to its orbital plane](https://i.sstatic.net/FXXLj.gif)](https://i.sstatic.net/FXXLj.gif)

and is, in fact, not far from what Uranus is doing.

The animation above was produced using Mathematica. The camera is above the plane of the planet's orbit, but not directly above the star. The rings are perpendicular to the plane of the orbit. Because the camera is off-center, we see a little bit of the side of the rings. Because the camera is at a finite distance, the angle between the plane of the rings and the line of sight from the camera varies along the orbit.

On the other hand, the animation shown below is physically impossible. Conservation of angular momentum prohibits it:

[![Animation of an impossible planet with rings always sideways to the sun](https://i.sstatic.net/HfVYb.gif)](https://i.sstatic.net/HfVYb.gif)

The ring is on the plane of the orbits of the particles the ring consists of, and (the direction of the normal of) this plane does not change during the orbit of the planet. Initially I thought that the ring would automatically be on the plane of the equator of the planet. Which is the case with Saturn's main rings and those of Uranus. However, [as explained here](https://astronomy.stackexchange.com/a/839/2342), there is no law of physics that would make this necessary. Even Saturn has a thin faint ring in a different orientation.

My limited understanding is that the origin of the ring plays a role. If a ring consists of the remains of a former satellite, then it will follow whatever orbit that satellite had. On the other hand, if the ring was formed together with the planetary system, or even ejecta from the forming planet, then it feels natural that the ring should be exactly on the equatorial plane.

We need an astronomer to give more details. After taking a peek at Wikipedia I suspect that a ring on the equatorial plane may be more stable. Particularly, if/when "shepherd moons" need to be present to keep the ring intact. Obviously the satellites tend to be near the equatorial plane of the mother planet. May be the gravity of the remaining satellites would perturb a ring in some other orientation more severely, meaning that it would not last long?

> **Comments:**
> **username_5**: What if this planet was tidally locked to the host star?  
> **username_4**: @fasterthanlight Then the host star is on the equatorial plane of the planet, right? Implying that so are the rings (if any can survive under the circumstances). The axis of the planet is perpendicular to the plane of the ring.  
> **username_4**: Actually I'm no longer sure about that. Anyway, the direction of the normal of the plane of the ring should be (near) constant, a tidal lock notwithstanding. So it would still be the situation in the top animation. And I think that the tidal forces of the star are strong enough to lock the planet, then they would also break apart the ring. I'm afraid I don't know.  
> **username_6**: The second case is not as impossible as it may seem. In fact, the rings follow a Sun synchronous orbit https://en.wikipedia.org/wiki/Sun-synchronous_orbit which is a very real thing.  
> **username_7**: Continuation of this question: https://astronomy.stackexchange.com/questions/40820/are-there-any-planetary-ring-system-other-than-phoebe-ring-not-aligned-to-the  
> **username_8**: @Pere 1- The rings typically follow the equator of the planet (due to angular momentum conservation) if, as the more common case, they are formed from protoplanetary dust. The sun synchronous orbit you mentioned would be for the planet, then this means that the planet's orbit and rotation, and consequently the rings, would be in the same plane (so, all parallel). The case you mentioned, of the rings being sun synchronous, saying the second case would be possible, defy linear/angular momentum conservation. But props to Jyrki  
> **username_8**: 2- To understand that it is not possible (or at least, in the planetary case, nearly impossible, but possible as in a thought experiment), just see how the rings move in relation to the planet, they spin around the planet in an awkward manner. Instead of the case like Saturn, where they spin in a disk (or like a hockey puck on ice), each particle of the rings has its own orbit, and the rings spin like a spinning coin on a table with the orbit time of the ring, being the same as the planet's orbit time. That is just weird. In this case you cannot add spin like the one of Saturn's rings...3  
> **username_8**: 3- as doing so means you create a cloud of dust, where all the particles collide and slowly coalesce into the actual plane allowed by the angular momentum, which is nothing like the case of a star-synchronous orbit  that you described. In other words, a ring system in a star-synchronous orbit is a highly (mega hyper) unstable equilibrium point.  
> **username_4**: @Pere An interesting possibility. At some point I had included a parenthetical remark *precession is possible, but we ignore that*. Then I removed it for I thought it would be confusing. Anyway, I'm not acquainted well enough with celestial mechanics to be able to tell whether a sizable ring can stably follow the kind of orbit you had in mind.  
> **username_4**: The point being that I did not know that fast enough precession could be feasibly achieved. What was the period with the Earth's axis again? 26000 years?  
> **username_8**: I was thinking about this again last night and noticed I made a mistake, that the parts on the rotation axis (the coin on table type) actually have no orbital speed, and would just fall onto the planet, secondly, the orbits are around the center of mass of the planet, not an axis (as in, of course you have an axis of rotation, but the projection of the rotation is on one point, not along the axis), meaning that kind of orbit is not possible  
> **username_8**: regarding precession and all other effects that come from more than 2 body mechanics, I am also not versed enough into that, but for sure that angular and linear momenta would not allow the case where the rings would align with the rotating plane including the star-planet line in the perpendicular of the orbit  
> **username_9**: Triton is closer to Neptune than the moon is to Earth. It orbits in the opposite direction of Neptune's spin and precesses between about 7 degrees and 53 degrees from the plane of Neptune's rotation. A Wikipedia source predicts that in less than 4 billion years Triton will be within the Roche limit an will break up to form a ring system. Therefore, Neptune will have rings that will not only be non-equatorial, but possibly still precess.  
> **username_4**: @Ilmari Exactly what you did to the GIFs to make them repeat indefinitely? It is a bit of a puzzle to me. Some of my old animated GIFs in Math.SE do loop infinitely, but the new ones won't. Even if I specify the parameter in Mathematica to Inifinity. I have a vague recollection that there was a SW change at some point, but I was never up to speed with that.  
> **username_10**: @JyrkiLahtonen: GIF animations have a loop count setting; if it's 0, the animation loops forever. A lot of GIF editing software allows changing the setting; I think I used [gifsicle](http://www.lcdf.org/gifsicle/). [Here's a few other options.](https://superuser.com/questions/159212/how-do-i-make-an-existing-animated-gif-loop-repeatedly)  
> **username_4**: @IlmariKaronen Apparently you managed it, but tinkering with the `AnimationRepetitions` parameter with Mathematica should do the same but won't. Irrespective of whether I set that parameter to $7$, $\infty$, or $0$. The animation is shown in browser exactly twice. This before it gets anywhere near imgur and their stuff. I thought the issue is browser related. Or a site policy even? I recall a thread where it was announced that the number of repetitiions was limited on purpose because users were abusing it. I thought you know some dirty tricks.  
> **username_4**: FWIW Mac OS X tools are of no use to me. I'm on Windows, for better or for worse :-)  
> **username_4**: @IlmariKaronen I learned that it is a bug in Mathematica, introduced in version 11 that I'm unlucky to own. [A fix](https://mathematica.stackexchange.com/a/238597/1155), kind of.  
> **username_10**: @JyrkiLahtonen: Gifsicle is cross-platform. [Here's a Windows build.](https://eternallybored.org/misc/gifsicle/)  
> **username_4**: Thanks @IlmariKaronen  

---

