No one knows how many stars there are. Each galaxy has millions, or billions, or even trillions of stars, and there are trillions of galaxies.

This section on stars will cover

1. What is a star, how does it form and make its energy?
   Stars are large burning spheres of gas. They form from clouds of dust and gas when gravity begins to condense the cloud smaller and smaller. How long a star can burn (lives), depends on the mass of the star. Smaller mass stars burn longer, live longer than the larger more massive stars.
2. What is the lifecycle of a star?
   Gas and dust to white dwarfs and black holes.
3. The H-R Diagram
   Color, temperature, and luminosity (brightness)
4. Star Vocabulary

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Galaxies       Stars      Solar System        Earth’s Motion