| A | B |
|---|
| magnitude | a measure of the brightness a star appears to have |
| absolute magnitude | the amount of light a star really gives off |
| H-R diagram | a chart that describes the colors of the stars and the amount of light they give off |
| main sequence stars | most of the stars we see, which fall along one line in an H-R diagram |
| giant stars | very bright, large stars that are fairly cool |
| white dwarfs | hot, very small stars |
| supergiants | very large stars |
| nova | a very bright star formed when a read giant explodes off its outer layer |
| black dwarf | a small, cold, dark body formed when a star uses up all its energy |
| black hole | a star whose matter fell inward into a very small space |
| binary star | two stars that move around each other |
| Mizar | the binary star in the handle of the Big Dipper |
| eclipsing binary star | a binary star having one star that blocks the light of the other |
| pulsating star | a variable star that changes in size and brightness in a regular manner |
| nebula | a large cloud of gas and dust that reflects light |
| galaxy | a group of many stars |
| spiral galaxy | a group of stars that is shaped like a pancake with arms branching out from the center |
| elliptical galaxy | a small group of stars shaped like a round or flattened ball |
| irregular galaxy | a small group of stars with no definite shape |
| Milky Way galaxy | a spiral galaxy containing the moon, the sun and all its planets, and all the stars we can see with the unaided eye |
| nucleus | the center of the Milky Way galaxy, made up of about 80 billion stars |
