1. 1. Describe 3 things you already know about stars.

2. 2.What Are Stars?
a. A star is a large celestial body that is composed of hot plasma and that emits light; the sun is a typical star.
b. The Sun, our closest star, is 93 million miles from Earth. ( 150 million kilometers)
c.The next closest star is 4.3 light years away.
d. By mass, the Sun is 71 % Hydrogen, 27% helium and the rest heavier elements. This is similar to the composition of the universe.
e. The Sun is about 4.6 billion years old.

3. 3. Sun’s Energy
a. The Sun, like all stars, are driven by nuclear fusion reactions.
b. The core of a star is extremely hot, extremely dense, and under extreme pressure.
c. Nuclear fusion takes place in the core of a star.
d. The Sun’s nuclear fusion combines the nuclei of hydrogen atoms to form a helium atom.

4. 4. Stellar Equilibrium.
The Sun is in stellar equilibrium. The inward force of gravity is balanced by the outward force of gas pressure caused by the Sun’s high core Temperature.

5. 5. What is a Light year? A light-year is how astronomers measure distance in space. It’s defined by how far a beam of light travels in one year – a distance of six trillion miles or 9 trillion kilometers.

6. Where are most stars located on the HR Diagram?
Which color stars are the hottest and which are the coolest?

7. Star types.
Nebula – a cloud of gas and dust in space that is the birthplace of star.
Protostar – young stars that are too small to fuse hydrogen.

8. Main Sequence Star – A middle age star that is fusing hydrogen into helium. EX: Sun
Red Giant and Super Giants – Older star running out of hydrogen and starting to fuse helium and others. Expanding.

9. Supernova – Exploding star.
White Dwarf – A dyeing star. No ar fusion but still hot enough to glow.
Black Dwarf – Dead star. Too cold to glow.
Neutron Star – Leftover core of a supernova. Dense.
Black hole – Leftover core of supernova; so dense that light cannot escape

10. 7. Draw the Life Cycle of our Sun.
8. Draw the Life Cycle of a Massive Star.
9. Use the terms to label the HR diagram.

11. Black Hole (Artist Rendition)
White Dwarf
Black Dwarf

12. Practice using the HR Diagrams on your own!