What do you mean by galaxy
Answers
a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction
Galaxies are the groups of mainly heavenly body such as Stars, Planets, Asteroids, Blackholes, nebula, White holes, Warm holes, etc. Which are bound together with their own Gravity. The center of the Galaxy is either a Supermassive Black hole or Warm holes or a group of stars or neutron stars.Every Galaxy has abundant hydrogen, so it is possible that on the surfaces of the planets of other than earth we can find Hydro-Carbon that is the sign of life. We can even find it under the surface. And maybe theAliens won't be similar and simple as we think. I think the theory about alien life that states that the humans are the aliens, Is false.