Nuclear Fusion

A Nuclear Fusion is when nuclear reaction inside a star change two hydrogen gas molecules into a helium molecule.

H-R Diagram

The H-R Diagram is to classify stars according to their luminnosity, spectral type, color, temperature and evolutionary stage.

Type of stars

 They are 4 type of star, they are White Dwarf, Main sequence, Supergiants and Giants.

What is a star?

 A star are very huge with hot gas, they look small because they are too far away, the hotter star are made by nuclear fusion, also star has lots of different color and size.