Physics, Astronomy & Cosmology / Re: Orbiting or descending into the black hole at the centre of the Milky Way?« on: 27/11/2022 20:49:35 »
Quote from: bored chemist
Mainly the MW is in orbit around itself.And the mass of the Milky way is dominated by the (so far) invisible Dark Matter halo.
Quote from: OP
it looks like the stars are swirling down into the black holeOut in the fringes (where we live), the stars are well-separated, most of the stars are in a fairly thin disk, have fairly circular orbits, and and have roughly the same angular velocity. So they won't interact very strongly with each other.
However, in the central bulge, stars are closely spaced, they have wildly different orbital planes, and the ones we can see near the central black hole have rather elliptical orbits, so the stars will transfer angular momentum between each other.
Some of these gravitational interactions will "cancel" angular momentum (if the stars have different orbital axes).
I expect that this will result in the central bulge flattening out over time - but the average distance from the central black hole will then be less than it is now. When stars are moving in a disk, they will have fairly stable orbits.
...that is, until the central black hole merges with another black hole; the incoming black hole will add angular momentum into the system on an entirely different axis, and once again send the stars off in all directions.
Quote from: OP
it looks like the stars are swirling down into the black holeYou inferred this from looking at a still image, and imagining the galaxy as a drain emptying in a whirlpool. This is not what "Whirlpool Galaxy" means.
The Gaia space probe has been able to measure the velocity of stars in the Large Magellanic Cloud, and it is showing the stretching associated with being spaghettified by its close approach to the Milky Way. But the orbits are still roughly elliptical, rather than converging on the central black hole (if it has one...)
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