Stars differ in size color temperature brightness and age.
Scientist know that the color of a star indicates the stars temputre. Red Stars are the coolest and blue stars are the hottest.
Scientist learn what stars are made of by studying chemical the light from stars. When a chemical emits a light only some colors show up.
Stars are now classified by how hot they are. Class O are blue. Class M stars are red.
Large groups of stars dust and gas are called in the galaxies.
The Milky Way is a spiral galaxy.an irregular Galaxy has no shape.
