The life of galaxies

[WallyWeet]

Do galaxies wither and die? Are they subject to the Second Law? Or do they forever renew and last forever? It seems all the matter in the universe deteriorates, do galaxies?

[neufer]

Do galaxies wither and die? Are they subject to the Second Law? Or do they forever renew and last forever? It seems all the matter in the universe deteriorates, do galaxies?

We barely understand Dark Matter & Dark Energy and you're asking for long term forecasts
(Or were they rhetorical questions?)

[geckzilla]

I think he really wants to know and I think it's safe to say the answer is that we don't know. Didn't they used to think that elliptical galaxies are younger than spiral galaxies? I seem to remember reading somewhere that now the conclusion is that spiral galaxies evolve into elliptical ones. Oh, who knows. Here's a pertinent Wikipedia link:
http://en.wikipedia.org/wiki/Galaxy#Future_trends

[RJN]

Yes, galaxies wither and die. Yes, galaxies obey the second law of thermodynamics, but matter falling in might appear to violate it as part of what is called the Gravothermal Catastrophe. See, for example, http://arxiv.org/abs/cond-mat/0204315 .

In the long run, galaxies are collapsing on the inside while at the same time expelling stars (and dark matter) to the outside. It's just that the time scale for this collapse is very very long, usually much longer than the present age of the universe. In the short run, though, galaxies are colliding, absorbing smaller galaxies, sometimes renewing themselves with the new mass, and sometimes changing galaxy types.

[geckzilla]

Well slap me silly and call me a crackpot. Apparently we do know.