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Unit 2
Solar system
| Term | Definition |
|---|---|
| solar system | The solar system is the collection of large and small bodies that orbit our central star, the sun. |
| planet | A planet is a spherical body that orbits the sun. |
| star | A star is a large celestial body that is composed of gas and emits light. |
| galaxy | A galaxy is a large collection of stars, gas, and dust that is held together by gravity. |
| light-year | A light-year is the distance that light travels through space in 1 year. |
| universe | The universe can be defined as space and all the matter and energy in it. However, this definition does not tell us about the structure of the universe. |
| apparent magnitude | A star is a large celestial body that is composed of gas and emits light. |
| luminosity | When astronomers use the word luminosity, they mean the actual brightness of a star. |
| absolute magnitude | Absolute magnitude is a measure of how bright a star would be if the star were located at a standard distance. |