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Saturn's rings will never clump together, because they are within the Roche limit. Which makes me wonder if a star could have rings that are kept from clumping together due to tidal forces. Have any ring systems been observed within the Roche limit of other stars?

The answers to this question consider rings in a more general sense. I would like to know specifically about rings around a star that exist due to the same mechanism as Saturn's rings.

usernumber
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  • By "same mechanism" do you mean a ring of any kind of material of any source, as long as it is inside the star's Roche limit, or do you mean a ring that was formed from material in the same way that Saturn's ring was formed? – uhoh Jan 30 '20 at 11:22
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    A ring within the Roche limit. It doesn't have to be made up of the same material – usernumber Jan 30 '20 at 13:36
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    Perhaps for small cool stars and brown dwarfs. I imagine for sun-like stars dust and small bodies inside the Roche limit would be vaporized, and wind and radiation pressure would drive them away. – antlersoft Jan 30 '20 at 16:45
  • I don't see how tidal forces come into play, as that only applies to a single object of nonhomgeneous density. – Carl Witthoft Jan 30 '20 at 19:43
  • I'm inclined to say yes, though I'm not sure how common they would be. As @antlersoft points out, a key factor would be not too much radiation, so maybe only the smallest red dwarfs or brown dwarfs if you want to call them stars. The high density of those small stars would extend the possible range of a ring system too. I'm sure they're out there for very low mass stars. I don't know if we have the telescopes to confirm that, especially since low mass stars often tend to be more variable in brightness. – userLTK Jan 30 '20 at 20:24
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    I would imagine that the various combinations of radiation pressure, stellar wind pressure, Poynting-Robertson drag and the Yarkovsky effect would tend to deplete a ring system fairly rapidly. –  Jan 30 '20 at 22:47
  • Possible duplicate: https://astronomy.stackexchange.com/questions/12935/can-a-star-have-a-ring-system?rq=1 Unless the asker means a ring like Saturn's ice ring, in which case I'm leaning towards no as an answer. – userLTK Feb 01 '20 at 05:17
  • Another possible duplicate: https://astronomy.stackexchange.com/q/17814/24157 - though that question is framed around brown dwarfs and the existing answer talks about circumstellar discs rather than ring systems within the Roche limit. –  Feb 04 '20 at 22:41

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As noted in the other question, stars can form rings around them. We call them circumstellar disc. But can stars can have "Saturn-like" rings that had a formation mechanism similar to Saturn (which are thought to be pieces of comets, asteroids or shattered moons that broke up before they reached the planet, torn apart by Saturn's powerful gravity)? The answer is "speculative". However, I found two cases:

  1. LSPM J0207+3331, a white dwarf is thought to have rings. The reason is unknown but scientists speculates that:

    [...] some white dwarfs — between one and four percent — show infrared emission indicating they’re surrounded by dusty disks or rings. Scientists think the dust may arise from distant asteroids and comets kicked closer to the star by gravitational interactions with displaced planets. As these small bodies approach the white dwarf, the star’s strong gravity tears them apart in a process called tidal disruption.

    The debris forms a ring of dust that will slowly spiral down onto the surface of the star.

  2. HR 4796A

Nilay Ghosh
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