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The solar system
Unit 3
| Term | Definition |
|---|---|
| Solar system | A collection of planets, moons, asteroids, comets, and other objects that orbit a star |
| Planet | A large object that orbits a star and has cleared its orbit of other debris. |
| Star | A massive ball of hot gas that produces light and heat through nuclear fusion. |
| galaxy | A huge system of stars, gas, dust, and dark matter held together by gravity. |
| Light-year | The distance that light travels in one year, about 5.88 trillion miles |
| Universe | All of space and everything in it, including galaxies, stars, planets, and matter. |
| Apparent magnitude | How bright a star appears from Earth. |
| Juminosity | The total amount of energy a star actually gives off per second. |
| absolute magnitude | How bright a star would appear if it were at a standard distance of 10 parsecs (32.6 light-years) from Earth. |