The "main sequence".
The young star stage because at that stage, stars are just burning, no interruptions or disturbances
what is the third stage of the star cycle
dust
stellar nebula
No, it's a possible stage in the life cycle of a star.
You can tell by its size and/or color.
Protostar!
Altair is still in the main sequence stage of a stars life. See related link for more information.
it doesn't.......
Formation of the star out of a giant cloud of gas and dust.
White Dwarf then Black Dwarf=Dead Star
WHITE DWARF ;p