The Universe - Galaxies
Galaxies are giant groups of millions or even trillions of stars. Our own galaxy is the Milky Way.
There may be 20 trillion galaxies in the universe.
Only three galaxies are visible to the naked eye from Earth besides the Milky Way - the Large and Small Magellanic clouds, and the Andromeda galaxy.
Although galaxies are vast, they are so far away that they look like fuzzy clouds. Only in 1916 did astronomers realize that they are huge star groups.
Spiral galaxies are spinning, Catherine-wheel-like galaxies with a dense core and spiralling arms.
Barred spiral galaxies have just two arms. These are linked across the galaxy's middle by a bar from which they trail like water from a spinning garden sprinkler.
Elliptical galaxies are vast, very old, egg shaped galaxies, made up of as many as a trillion stars.
Irregular galaxies are galaxies with no obvious shape. They may have formed from the debris of galaxies that crashed into each other.
Galaxies are often found in groups called clusters. One cluster may have 30 or so galaxies in it.