The Stars

1. What is a star ?

A star is a luminous large ball of hot gas. Because they are light years far away from us, so they look small. But in fact many stars are bigger and brighter than the sun. The center of a star has nuclear fusion to make heat and energy.There are lots of different colors and sizes of stars.


2. Types of Stars

White Dwarf

Giant

 The 4 types of stars: Super Giant, Giant, Main Sequence and White Dwarf. Super Giant stars are large middle age stars, they have medium temperature. Also they are bright stars. Giant stars are large middle age stars. they are irregular range stars on temperature, luminosity and color. Main Sequence stars are medium middle age stars, they are cold and have large range luminosity. White Dwarf are small young stars, they are hot but dim luminous. 

Supergiant

Main Sequence

3. H-R Diagram

The Hertzsprung - Russell diagram is a graphical tool use to classify stars based on their luminosity, spectral class, color, temperature and evolutionary stage.


4. Nuclear Fusion

Stars are made in giant clouds of dust and gas called a stellar nebula. The gravity cause of the cloud get smaller and it become hotter. When the cloud is hot enough, a star is formed while the nuclear reaction will occur in the middle of the cloud. The nuclear reaction is change two hydrogen gas molecules into a helium molecule to make energy. This process is known as nuclear fusion.



5. The Life Cycle of a Star

There are three types life cycle of a star. They all start from stellar nebula which is a giant cloud with dust and gas. Sun-like stars will become red giant. after that, it will become a cloud of dust and gas called planetary nebula, and then it will become white dwarf. After this, it will turn into a cold, dark object called black dwarf. Huge stars and Giant stars both will become red super giant, after they will pass through a giant explosion called supernova. At the end, huge stars will become a small, dense neutron star and Giant stars will become a dead star called black hole.