The universe is made up of giant groups of stars which are called galaxies. The galaxy it is a collection of stars, dust, and gas held together by gravity.
Una galaxy it contains millions of stars. The galaxies are in motion in the universe, and they are moving away from each other. Edwin Hubble showed that the universe was expanding. The earth belongs to the galaxy called the Milky Way.
All the galaxies they have wonderful and practically unique shapes. We don't know how many galaxies there are in the universe, scientists think there must be hundreds of thousands. Certain galaxies they have pretty names, like Milky Way, or Galaxia Andromeda, while others are simply numbered, with a relationship of letters and figures, such as the galaxy NGC 300.
https://www.youtube.com/watch?v=mJ47Uvf8c6E
All the galaxies they give the impression of being thrown randomly into the universe. Some are isolated, while others galaxies they are grouped in the same place in the universe.
The galaxies are in perpetual movement, and certain scientists think that certain galaxies eat others. For example, they think that galaxy Andromeda absorbed another galaxy, which would explain its double center.