The closest objects in extragalactic astronomy include the galaxies of the Local Group, which are close enough to allow very detailed analyses of their contents (e.g. supernova remnants, stellar associations).
[1] Research into distant galaxies (outside of our local group) is valuable for studying aspects of the universe such as galaxy evolution[2] and Active Galactic Nuclei (AGN) which give insight into physical phenomena (e.g. super massive black hole accretion and the presence of dark matter[3]).
A key interest in Extragalactic Astronomy is the study of how galaxies behave and interact through the universe.
Astronomer's methodologies depend — from theoretical to observation based methods.Galaxies form in various ways.
In most Cosmological ''N''-body simulations, the earliest galaxies in the cosmos formed in the first hundreds of millions of years.