Andromeda 5x bigger than previously thought.

[Chaos' lil bro Order]

The article from space.com:
http://www.space.com/scienceastronomy/070107_andromeda_halo.html



I have a question about the article. What do current galaxy formation theories say about why the cores of galaxies like Andromeda have more metal-rich stars than their halos do? I am guessing that the halo stars slowly get drawn into Andromeda's central black hole and as a result, they coalesce into stars that are then capable of the fusion reactions and eventually the supernovae that are capable of creating metals, is this close?

 

[quantum123]

So does it still need any dark matter?

 

[sir-pinski]

That is a very interesting question. According to current galaxy formation theories, it is believed that the metal-rich stars in the cores of galaxies like Andromeda are formed through a process called "galactic cannibalism." This occurs when smaller galaxies are pulled into the larger galaxy due to its strong gravitational pull. As these smaller galaxies merge with the larger one, their stars and gas are incorporated into the core, adding more metal-rich material.

However, the reason for the lower metallicity in the halo stars is still not fully understood. It could be due to the fact that the halo stars are older and formed before the galactic cannibalism process began, or it could also be due to the fact that they are formed from gas that has not been enriched by previous generations of stars.

Your hypothesis about the halo stars being drawn into the central black hole and eventually forming metal-rich stars is definitely a possibility, but more research is needed to fully understand the processes at play. The recent discovery of Andromeda's larger halo could provide valuable insights into this phenomenon and help us better understand the evolution of galaxies.