Galaxy
A galaxy is a mass of billions of stars.
The Milky Way is our galaxy, whom we can see a spiral arm during a clear night.
The closest spiral galaxy, and most probably looking alike ours, is Andromeda galaxy, also named M31 (from the Messier catalogue), located at about 3 millions light years from us.
Our galaxy owns two small galaxies that are in orbit and that are named the Small and the Large Magellanig Cloud (SMC & LMC), discovered by Magellan in 1519.
See light year, Messier, Magellan
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