<p>In a sense, that is what a <a href="https://en.wikipedia.org/wiki/Circumstellar_disc" rel="nofollow noreferrer">circumstellar disk</a> is.</p>

<p><a href="https://i.sstatic.net/gTiCB.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/gTiCB.jpg" alt="HL Tauri disk"></a></p>

<p><sub>Source: <a href="http://www.eso.org/public/archives/images/large/eso1436a.jpg" rel="nofollow noreferrer">European Southern Observatory (ESO)</a></sub></p>

<p>These are usually most noticeable around young stars as protoplanetary disks, disks that form planets. In the picture above, the gaps in the "rings" likely represent forming planets, similar to how the gaps in Saturn's rings indicate the presence of moons.</p>

<p>Our own star has a few "rings", though likely not as visually impressive: the asteroid belt, the Kupier belt, the scattered disk, and the Hills cloud.</p>

<p>That said, there are differences between these structures and the ring systems we are familiar with from planets. For example, rings are made of solid particles whereas protoplanetary disks contain a lot of gases. Rings may exist around "mature" planets, whereas protoplanetary disks represent an immature phase of planetary systems. Protoplanetary disks are not visible to the naked eye, whereas ring systems may be. In technical terms, a circumstellar disk is not a ring system. </p>

CC BY-SA 3.0
2016-08-05T13:25:54.100Z
The "Hills Cloud" idea is sort of a tweak on the Oort Cloud, right?
Fattie
CC BY-SA 3.0
2016-08-05T13:27:16.913Z
@JoeBlow Not exactly, it is also called the inner Oort Cloud. It is separate from the outer cloud. The Hills cloud is actually more disk-like, whereas the outer cloud is distributed in a more spherical pattern.
called2voyage
CC BY-SA 3.0
2016-08-05T13:28:11.663Z
Gotchya, cheers.
Fattie
CC BY-SA 3.0
2016-08-05T13:30:02.037Z
@JoeBlow Oh, and I should say *presumed* to be. Both clouds are merely theoretical at this point, we don't have a lot of direct evidence for them.
called2voyage
CC BY-SA 3.0
2016-08-07T23:00:30.633Z
I'm going to cry a small foul on this one cause a traditional ring system is mostly inside the Roche limit and a Circumstellar disk is mostly outside, so this is something in formation not a semi-permanent ring system.   Whether a star in it's main sequence can have a ring system is a tough question.  I would think it would have to be a very cold star.  A brown dwarf or just maybe a smaller luminosity or late in it's life red-dwarf.
userLTK
CC BY-SA 3.0
2016-08-08T13:23:46.690Z
@userLTK That's a fair criticism, but a traditional ring system is not permanent either, precisely *because* it is inside the Roche limit. Also, not all circumstellar disks are considered "something in formation", though protoplanetary disks certainly are.
called2voyage
CC BY-SA 3.0
2016-08-08T13:24:37.443Z
@userLTK And note, I did qualify with "in a sense". Though perhaps a few words on the Roche limit would be appropriate.
called2voyage
CC BY-SA 3.0
2016-08-08T15:51:50.413Z
@userLTK Worth noting: As stated in the question, my in-game discovery *was* a brown dwarf star.
Iszi
CC BY-SA 3.0
2016-08-08T15:59:38.923Z
Maybe a separate question needs to be addressed here: Aside from the nature of the central body, is there any particular difference in definitions between "planetary ring" and "circumstellar disk"? What I'm seeing feels more like the former.
Iszi
CC BY-SA 3.0
2016-08-08T16:03:51.497Z
@Iszi That's what is tough about brown dwarfs, and is why I answered as I did. Brown dwarfs are neither stars nor planets, but they are in between. Too small for hydrogen fusion, but they are not considered gas giants because they are large enough to sustain deuterium fusion.
called2voyage
CC BY-SA 3.0
2016-08-08T16:43:21.220Z
@called2voyage Good point. Still, the question remains what - if anything, other than the central body - really differentiates a "planetary ring" from a "circumstellar disk"?
Iszi
CC BY-SA 3.0
2016-08-08T16:55:00.257Z
Posted the terminology question separately: http://astronomy.stackexchange.com/questions/17845/difference-between-planetary-ring-and-circumstellar-disk?noredirect=1&lq=1 If the distance from the central body is a factor, I'll see what I can do to take in-game measurements. But I doubt that will be possible - it's likely that the space within the ring system (never mind the space inside of its inner radius) is too hot for me to fly in for long, if at all.
Iszi
CC BY-SA 4.0
2020-02-04T23:17:03.317Z
@called2voyage: Permanency of the rings inside and outside the Roche radius is not an issue. What counts is that in a PP Disc the dust you see will coalesce into planets on very short (<10 Myr) timescale, due to interactions with the present gas, while a ring system outside its hosts Roche, has no gas, and hence wouldn't form larger bodies. Your comparison of PPDiscs with ring systems is physically wrong.
AtmosphericPrisonEscape
CC BY-SA 4.0
2020-02-04T23:21:34.487Z
@AtmosphericPrisonEscape I'm still not sure how that makes an appreciable difference to a lay human observer. Is it physically the same as a ring system? No. Would a layperson look at the star during that stage and say "it has rings"? I would say yes.
called2voyage
CC BY-SA 4.0
2020-02-05T00:15:33.997Z
@called2voyage: ??? How is 'what you see' relevant? The only thing that matters is physics. That is how we categorize objects. Btw you don't 'see' HL Tau like this. This is sub-mm emission, invisible to the eye.
AtmosphericPrisonEscape
CC BY-SA 4.0
2020-02-05T00:54:49.160Z
@AtmosphericPrisonEscape It's relevant because the question is basically, "I see what looks like rings here, is something looking like this a thing?" And I'm counting seeing a visual representation of sensor data as seeing, just like we would when looking at a phone camera image that captured infrared light.
called2voyage
CC BY-SA 4.0
2020-02-05T07:00:46.360Z
Rings are made of  solid particles. (I would say). This disc (for that is what it is) will still have plenty of gas.
ProfRob
CC BY-SA 4.0
2020-02-05T11:10:15.387Z
@RobJeffries I appreciate and do not disagree with the technical definitions, but I don't think a good answer to a layperson's question can ignore the fact that no such distinction between rings  and discs in plain language exists. That said, if the criticism here is that my answer does not do enough to educate the user on what a ring system is to an astronomer, I think that is fair, as all I do to qualify the statement is the phrase "in a sense". So I could probably add some more language to clarify that these terms have specific meanings in astronomy that might differ from a common understan
called2voyage
CC BY-SA 4.0
2020-02-05T11:10:34.663Z
*understanding.
called2voyage
CC BY-SA 4.0
2016-08-04T20:41:09.920Z
2020-02-11T16:15:12.443Z
2020-02-11T16:15:12.443Z
called2voyage
<p>The other night, while playing Elite: Dangerous, I came across a rather strange celestial body - one I never imagined possible.</p>

<p>It was a Brown Dwarf star with a <em>very large</em> ring.</p>

<p><a href="https://i.sstatic.net/67Pqd.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/67Pqd.png" alt="enter image description here"></a></p>

<p>Is something like this even remotely possible? Have such objects actually been seen?</p>

<p>It was also quite interesting that this star wasn't even the primary star in the system. It was orbiting a larger star (blue-white, I think), along with several planets.</p>

<p><a href="https://i.sstatic.net/mnzf8.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mnzf8.png" alt="enter image description here"></a></p>

CC BY-SA 3.0
2016-08-11T13:32:19.930Z
Now that I see the pictures, this looks somewhere in between a ring system and a circumstellar disk...which is appropriate given that the central body is a brown dwarf.
called2voyage
CC BY-SA 3.0
2016-08-11T14:45:09.643Z
@called2voyage This goes back to nailing down the definition of the two terms - how's it "in between"? Looks pretty solidly on the "ring" side to me.
Iszi
CC BY-SA 3.0
2016-08-11T14:46:08.360Z
It is difficult to tell from a picture, but this appears to extend well beyond the Roche limit.
called2voyage
CC BY-SA 3.0
2016-08-11T14:46:42.037Z
Compare to the size of Saturn's rings.
called2voyage
CC BY-SA 3.0
2016-08-11T14:49:15.523Z
If the Roche limit is really important to distinguishing the ring types, someone should address it in the definition question. As for measuring the exact difference, I'll see what I can do if/when I get back to the system. No guarantees though. (AFAIK the only way to really measure distance in-game is by checking the range of an object from the ship - and that is still a heat-radiating body in the middle there.)
Iszi
CC BY-SA 3.0
2016-08-11T15:18:54.033Z
See my reply to your other question. Apparently, it could be called a circumstellar disk *or* a ring system, as long as it contains solid material (a requirement for ring systems).
called2voyage
CC BY-SA 4.0
2020-02-10T16:39:43.847Z
A brown dwarf can be a lot denser than Saturn, perhaps nearly 100 times the density.   That should extend the Roche limit outwards as far as (cube root of 100) about 4.6 times.   That ring system in that image might be possible.
userLTK
<star><planetary-ring>
Do/Can Ringed Stars Exist?
Iszi
# Do/Can Ringed Stars Exist?

(Asked by: username_0 on 2016-08-04)

The other night, while playing Elite: Dangerous, I came across a rather strange celestial body - one I never imagined possible.

It was a Brown Dwarf star with a *very large* ring.

[![enter image description here](https://i.sstatic.net/67Pqd.png)](https://i.sstatic.net/67Pqd.png)

Is something like this even remotely possible? Have such objects actually been seen?

It was also quite interesting that this star wasn't even the primary star in the system. It was orbiting a larger star (blue-white, I think), along with several planets.

[![enter image description here](https://i.sstatic.net/mnzf8.png)](https://i.sstatic.net/mnzf8.png)

**Tags:** star, planetary-ring
> **Comments:**
> **username_1**: Now that I see the pictures, this looks somewhere in between a ring system and a circumstellar disk...which is appropriate given that the central body is a brown dwarf.  
> **username_0**: @called2voyage This goes back to nailing down the definition of the two terms - how's it "in between"? Looks pretty solidly on the "ring" side to me.  
> **username_1**: It is difficult to tell from a picture, but this appears to extend well beyond the Roche limit.  
> **username_1**: Compare to the size of Saturn's rings.  
> **username_0**: If the Roche limit is really important to distinguishing the ring types, someone should address it in the definition question. As for measuring the exact difference, I'll see what I can do if/when I get back to the system. No guarantees though. (AFAIK the only way to really measure distance in-game is by checking the range of an object from the ship - and that is still a heat-radiating body in the middle there.)  
> **username_1**: See my reply to your other question. Apparently, it could be called a circumstellar disk *or* a ring system, as long as it contains solid material (a requirement for ring systems).  
> **username_2**: A brown dwarf can be a lot denser than Saturn, perhaps nearly 100 times the density.   That should extend the Roche limit outwards as far as (cube root of 100) about 4.6 times.   That ring system in that image might be possible.  

---

## 1 answers

### Answer by username_1 on 2016-08-04. Score: 14

In a sense, that is what a [circumstellar disk](https://en.wikipedia.org/wiki/Circumstellar_disc) is.

[![HL Tauri disk](https://i.sstatic.net/gTiCB.jpg)](https://i.sstatic.net/gTiCB.jpg)

Source: [European Southern Observatory (ESO)](http://www.eso.org/public/archives/images/large/eso1436a.jpg)

These are usually most noticeable around young stars as protoplanetary disks, disks that form planets. In the picture above, the gaps in the "rings" likely represent forming planets, similar to how the gaps in Saturn's rings indicate the presence of moons.

Our own star has a few "rings", though likely not as visually impressive: the asteroid belt, the Kupier belt, the scattered disk, and the Hills cloud.

That said, there are differences between these structures and the ring systems we are familiar with from planets. For example, rings are made of solid particles whereas protoplanetary disks contain a lot of gases. Rings may exist around "mature" planets, whereas protoplanetary disks represent an immature phase of planetary systems. Protoplanetary disks are not visible to the naked eye, whereas ring systems may be. In technical terms, a circumstellar disk is not a ring system.

> **Comments:**
> **username_3**: The "Hills Cloud" idea is sort of a tweak on the Oort Cloud, right?  
> **username_1**: @JoeBlow Not exactly, it is also called the inner Oort Cloud. It is separate from the outer cloud. The Hills cloud is actually more disk-like, whereas the outer cloud is distributed in a more spherical pattern.  
> **username_3**: Gotchya, cheers.  
> **username_1**: @JoeBlow Oh, and I should say *presumed* to be. Both clouds are merely theoretical at this point, we don't have a lot of direct evidence for them.  
> **username_2**: I'm going to cry a small foul on this one cause a traditional ring system is mostly inside the Roche limit and a Circumstellar disk is mostly outside, so this is something in formation not a semi-permanent ring system.   Whether a star in it's main sequence can have a ring system is a tough question.  I would think it would have to be a very cold star.  A brown dwarf or just maybe a smaller luminosity or late in it's life red-dwarf.  
> **username_1**: @userLTK That's a fair criticism, but a traditional ring system is not permanent either, precisely *because* it is inside the Roche limit. Also, not all circumstellar disks are considered "something in formation", though protoplanetary disks certainly are.  
> **username_1**: @userLTK And note, I did qualify with "in a sense". Though perhaps a few words on the Roche limit would be appropriate.  
> **username_0**: @userLTK Worth noting: As stated in the question, my in-game discovery *was* a brown dwarf star.  
> **username_0**: Maybe a separate question needs to be addressed here: Aside from the nature of the central body, is there any particular difference in definitions between "planetary ring" and "circumstellar disk"? What I'm seeing feels more like the former.  
> **username_1**: @Iszi That's what is tough about brown dwarfs, and is why I answered as I did. Brown dwarfs are neither stars nor planets, but they are in between. Too small for hydrogen fusion, but they are not considered gas giants because they are large enough to sustain deuterium fusion.  
> **username_0**: @called2voyage Good point. Still, the question remains what - if anything, other than the central body - really differentiates a "planetary ring" from a "circumstellar disk"?  
> **username_0**: Posted the terminology question separately: http://astronomy.stackexchange.com/questions/17845/difference-between-planetary-ring-and-circumstellar-disk?noredirect=1&lq=1 If the distance from the central body is a factor, I'll see what I can do to take in-game measurements. But I doubt that will be possible - it's likely that the space within the ring system (never mind the space inside of its inner radius) is too hot for me to fly in for long, if at all.  
> **username_4**: @called2voyage: Permanency of the rings inside and outside the Roche radius is not an issue. What counts is that in a PP Disc the dust you see will coalesce into planets on very short (<10 Myr) timescale, due to interactions with the present gas, while a ring system outside its hosts Roche, has no gas, and hence wouldn't form larger bodies. Your comparison of PPDiscs with ring systems is physically wrong.  
> **username_1**: @AtmosphericPrisonEscape I'm still not sure how that makes an appreciable difference to a lay human observer. Is it physically the same as a ring system? No. Would a layperson look at the star during that stage and say "it has rings"? I would say yes.  
> **username_4**: @called2voyage: ??? How is 'what you see' relevant? The only thing that matters is physics. That is how we categorize objects. Btw you don't 'see' HL Tau like this. This is sub-mm emission, invisible to the eye.  
> **username_1**: @AtmosphericPrisonEscape It's relevant because the question is basically, "I see what looks like rings here, is something looking like this a thing?" And I'm counting seeing a visual representation of sensor data as seeing, just like we would when looking at a phone camera image that captured infrared light.  
> **username_5**: Rings are made of  solid particles. (I would say). This disc (for that is what it is) will still have plenty of gas.  
> **username_1**: @RobJeffries I appreciate and do not disagree with the technical definitions, but I don't think a good answer to a layperson's question can ignore the fact that no such distinction between rings  and discs in plain language exists. That said, if the criticism here is that my answer does not do enough to educate the user on what a ring system is to an astronomer, I think that is fair, as all I do to qualify the statement is the phrase "in a sense". So I could probably add some more language to clarify that these terms have specific meanings in astronomy that might differ from a common understan  
> **username_1**: *understanding.  

---

