A galaxy is a collection of stars and other celesial bodies,which has a distinct identity.

It is basically group. In Astronomy A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly-understood component tentatively dubbed dark matter.
A galaxy is, by definition, any large collection of stars that can be recognized as a distinct physical entity. In terms of the number of stars, a small 'dwarf irregular' galaxy like the Small Magellanic Cloud, has about one billion stars in it, but there are even smaller systems that are recognized as galaxies such as the Leo I and II dwarf galaxies with about 1 million stars in them, and the Draco System with a few hundred thousand stars in it. The largest star cluster, a globular cluster called Messier 15 has about 6 million stars, so we see that for small galaxies, there is a blurring together of what we mean by a galaxy and a large star cluster. In addition to their mass and numbers of stars, a galaxy is a collection of stars and ...more

On sky where all planet forms star like appearence