Constellations contain stars that are easy to pick out in the night sky. Due to this, the constellations are made up of stars from within our own galaxy, the Milky Way, as they are close enough to be seen with the naked eye. Light from individual stars in other galaxies is too dim to be seen without the use of a telescope.
Although single stars from other galaxies can’t be seen with ours eye alone, some galaxies and nebula can be. For example, the Andromeda galaxy is a collection of over 1 trillion stars approximately 2.5 million light-years away. It can be seen as a fuzzy oval in the night sky, although you need a clear night in a rural area to see it.
Answered by Zoe Baily from the National Space Centre
Image credit Hillary Mathis, N.A.Sharp, NOAO, AURA and NSF