A star is a large balls of hot gas.they look small because they are a long away but many are bigger and brighter than the sun they have different colors and size of stars. Stars are made of gas and dust in a big cloud, cloud gets smaller because of the gravity as it become hotter,when it hot enough the Nuclear Reactions can start in the middle than it born .
There are four type of stars there are super Giants, Giants,Main sequence and white dwarfs, white dwarf is old star dim, small bright,and hot stars.
Nuclear Fusion is nuclear reaction inside a two a star change two hydrogen gas
molecules in helium molecule and it create energy.
Hertzsprung-Russel Diagram is a graphical that astronomers use to classify star according to their luminosity,spectral type color and temperatures.
