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unit-2 lesson 1-2
vocab terms
| Term | Definition |
|---|---|
| solar system | the sun and all of the planets and other bodies that travel around it |
| galaxy | a collection of stars dust and gas bound together by gravity |
| planet | a relatively large spherical body that orbits a star |
| light year | the distance light travels in one year about 9.46 trillion kilometers |
| star | a large celestial body that is composed of gas and that emits light |
| universe | space and all the matter and energy in it |
| luminosity | the actual brightness of an object such as a star |
| apparent magnitude | the brightness of a star as seen from earth |