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A friend called my attention to an interesting paper by Abe Loeb and David Spergel and somebody else. It seemed to raise unresolved issues about the DM and globular clusters.
Does anybody know the current mainstream thinking about this?
In case anyone is new to this, Loeb and Spergel are two of the top leaders in astronomy in the US---one at harvard and the other at princeton. The fact that they just wrote a paper about this is a hint that there is some interesting problem connected to it.
I don't know very much about this, but I will summarize what I think are the basics.
Globular clusters are roughly (sometimes oblate/elliptical) spheres of a few 100 thousand old stars within a radius of a few tens of light years.
We know they formed early in history because the stars are "metal-poor"---mostly H and He with very little heavier elements.
Milky has about 150 known GC. Some other galaxies have more, it varies.
The GC orbit the galaxy core, passing regularly through the plane of the galaxy. They go on highly elliptical orbits somewhat the way comets orbit the sun. Brief visit in close and then a long time way out, like 50 or 100 thousand LY from core, and then falling back in for another brief pass. Tidal forces tend to pull them apart during their time close to the core. We see them in various stages of disarray. Streamers of stars pulled off of them by tidal force.
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One puzzle is that GC do not seem to have any DM. Typically anyway. So how did they originally form?
AFAIK the current ideas of structure formation say that DM helped ordinary matter to cluster together and form stuff like stars and groups of stars and galaxies and groups of galaxies. There are impressive computer simulations showing how DM helped gather stuff and organize structures.
So did Globular Clusters USED to have Dark Matter that helped them to form into clusters but then later their DM was sucked out of them by tidal disruption? As they passed close to bigger concentrations of mass?
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Also someone suggested that DM might be ANNIHILATED by interaction with ordinary matter. But I don't think that is a mainstream idea. I never heard any theory of DM which would say that it is annihilated that way. But that is a separate question.
Does anybody know the current mainstream thinking about this?
In case anyone is new to this, Loeb and Spergel are two of the top leaders in astronomy in the US---one at harvard and the other at princeton. The fact that they just wrote a paper about this is a hint that there is some interesting problem connected to it.
I don't know very much about this, but I will summarize what I think are the basics.
Globular clusters are roughly (sometimes oblate/elliptical) spheres of a few 100 thousand old stars within a radius of a few tens of light years.
We know they formed early in history because the stars are "metal-poor"---mostly H and He with very little heavier elements.
Milky has about 150 known GC. Some other galaxies have more, it varies.
The GC orbit the galaxy core, passing regularly through the plane of the galaxy. They go on highly elliptical orbits somewhat the way comets orbit the sun. Brief visit in close and then a long time way out, like 50 or 100 thousand LY from core, and then falling back in for another brief pass. Tidal forces tend to pull them apart during their time close to the core. We see them in various stages of disarray. Streamers of stars pulled off of them by tidal force.
=============================
One puzzle is that GC do not seem to have any DM. Typically anyway. So how did they originally form?
AFAIK the current ideas of structure formation say that DM helped ordinary matter to cluster together and form stuff like stars and groups of stars and galaxies and groups of galaxies. There are impressive computer simulations showing how DM helped gather stuff and organize structures.
So did Globular Clusters USED to have Dark Matter that helped them to form into clusters but then later their DM was sucked out of them by tidal disruption? As they passed close to bigger concentrations of mass?
===============================
Also someone suggested that DM might be ANNIHILATED by interaction with ordinary matter. But I don't think that is a mainstream idea. I never heard any theory of DM which would say that it is annihilated that way. But that is a separate question.