Saw this article
https://phys.org/news/2023-02-solar.html
and now this one >https://arstechnica.com/science/2023/02/dwarf-planet-hosts-a-ring-thats-unexpectedly-far-from-the-planet/
The distance of the ring from the planet is seven times the planet's diameter.
It was believed that it would be impossible for rings to be found at that >distance, because it's beyond Roche's Limit.
Roche's Limit is a distance which marks the closest a moon can be to
its primary before tidal forces will break it up. Conversely, outside Roche's >Limit, not only will a ring not form from the breakup of a moon, but if a >ring somehow got there, the matter in the ring would clump together and coalesce into a satellite, it is believed.
The ring was discovered through an occultation event.
Roche's Limit is pretty settled basic physics, so it will be interesting
to see what explanation is found. But there are possibilities.
- the ring was very recently moved outwards from a previous location
within Roche's Limit, and it does not have long to survive;
- the ring is maintained by the gravitational influence of a "shepherd
moon" or something like that
And both the asteroid belt and the Kuiper Belt are well outside
the Sun's Roche Limit, so perhaps this ring doesn't quite meet
the definition of a ring?
John Savard
On Thursday, February 9, 2023 at 5:33:45 AM UTC-7, Quadibloc wrote:
On Thursday, February 9, 2023 at 12:06:52 AM UTC-7, Barry Schwarz wrote:
How can you calculate the Roche limit without knowing the masses of
the bodies involved?
The articles claim it's just three times the diameter of the primary body.And, of course, you are right: those articles are *wrong*.
Instead, the Roche limit is the radius of the primary, times the cube root
of twice the ratio of the density of the primary to that of the satellite.
So if the satellite has a low density, the Roche limit can be further out. But
if they're of equal density - a possibility, since Quaoar is quite small - instead
of three times the diameter, we get 1.26 times the radius of Quaoar.
How can you calculate the Roche limit without knowing the masses of
the bodies involved?
On Thursday, February 9, 2023 at 12:06:52 AM UTC-7, Barry Schwarz wrote:
How can you calculate the Roche limit without knowing the masses of
the bodies involved?
The articles claim it's just three times the diameter of the primary body.
On Thursday, February 9, 2023 at 5:40:34 AM UTC-7, Quadibloc wrote:
On Thursday, February 9, 2023 at 5:33:45 AM UTC-7, Quadibloc wrote:
On Thursday, February 9, 2023 at 12:06:52 AM UTC-7, Barry Schwarz wrote:
How can you calculate the Roche limit without knowing the masses of
the bodies involved?
The articles claim it's just three times the diameter of the primary body.
And, of course, you are right: those articles are *wrong*.
Instead, the Roche limit is the radius of the primary, times the cube root of twice the ratio of the density of the primary to that of the satellite.
So if the satellite has a low density, the Roche limit can be further out. But
if they're of equal density - a possibility, since Quaoar is quite small - instead
of three times the diameter, we get 1.26 times the radius of Quaoar.
No doubt what they're doing instead is calculating an upper limit for how
far out Roche's limit could be, and then noting that the ring is out beyond that. So one could assume Quaoar is made of pure nickel-iron, and that
the Roche's limit for something made of ice is what is of interest.
On Thursday, February 9, 2023 at 5:48:00 AM UTC-7, Quadibloc
wrote:
On Thursday, February 9, 2023 at 5:40:34 AM UTC-7, QuadiblocAh, there we are. Two mysteries explained with one stone!
wrote:
On Thursday, February 9, 2023 at 5:33:45 AM UTC-7, Quadibloc
wrote:
On Thursday, February 9, 2023 at 12:06:52 AM UTC-7, Barry
Schwarz wrote:
How can you calculate the Roche limit without knowing the
masses of the bodies involved?
The articles claim it's just three times the diameter of
the primary body.
And, of course, you are right: those articles are *wrong*.
Instead, the Roche limit is the radius of the primary, times
the cube root of twice the ratio of the density of the
primary to that of the satellite.
So if the satellite has a low density, the Roche limit can be
further out. But if they're of equal density - a possibility,
since Quaoar is quite small - instead of three times the
diameter, we get 1.26 times the radius of Quaoar.
No doubt what they're doing instead is calculating an upper
limit for how far out Roche's limit could be, and then noting
that the ring is out beyond that. So one could assume Quaoar is
made of pure nickel-iron, and that the Roche's limit for
something made of ice is what is of interest.
Obviously, Quaoar is actually a neutron star that has wandered
into our Solar System. This explains how it can have a ring so
far out... and it also means that Quaoar is Planet Nine!
Saw this article
https://phys.org/news/2023-02-solar.html
and now this one https://arstechnica.com/science/2023/02/dwarf-planet-hosts-a-ring-thats-unexpectedly-far-from-the-planet/
The distance of the ring from the planet is seven times the planet's diameter.
It was believed that it would be impossible for rings to be found at that distance, because it's beyond Roche's Limit.
Roche's Limit is a distance which marks the closest a moon can be to
its primary before tidal forces will break it up. Conversely, outside Roche's Limit, not only will a ring not form from the breakup of a moon, but if a ring somehow got there, the matter in the ring would clump together and coalesce into a satellite, it is believed.
The ring was discovered through an occultation event.
Roche's Limit is pretty settled basic physics, so it will be interesting
to see what explanation is found. But there are possibilities.
- the ring was very recently moved outwards from a previous location
within Roche's Limit, and it does not have long to survive;
- the ring is maintained by the gravitational influence of a "shepherd
moon" or something like that
And both the asteroid belt and the Kuiper Belt are well outside
the Sun's Roche Limit, so perhaps this ring doesn't quite meet
the definition of a ring?
John Savard
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