Stars

What is a star? Well, in astronomy, a star is a naturally occurring spheroid held together by self-gravity and maintained through nuclear fusion in its core. Stars are the reason why many planets and exoplanets orbit and have day and night cycles. Astronomers estimate that the universe contains between 10²² to 10²⁴ stars. However, stars of course aren't the largest occurring objects. Stars can form galaxies and clusters through the force of gravity, too.

Here are the topics for this unit:

Stellar Classification

Hertzsprung-Russell Diagram

Stellar Evolution