Answer:
Galaxies are sprawling systems of dust, gas, dark matter, and anywhere from a million to a trillion stars that are held unitedly by gravity. Nearly all large galaxies are believed to also contain supermassive black holes at their centers. In our galaxy, the Milky Way, the sun is just one of about 100 to 400 billion stars that spin around Sagittarius A, a supermassive black hole that holds as much mass as four million suns. Some of the galaxies receding from the Milky Way are ellipsoidal, like footballs. Galaxies can also be thin and flat with tentacle-like arms.
