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Universe & Space
| Term | Definition |
|---|---|
| galaxy | a system of billions of stars, together with gas and dust, held together. |
| star | a fixed luminous point in the sky, which is a large body like the sun. |
| planet | a celestial body moving in a elliptical orbit around a star. |
| moon | a natural satellite of any planet. |
| sun | the star around which earth orbits. |
| solar system | the collection of the 8 planets and their moons in orbit around the sun, together with smaller bodies in the form of asteroids, meteoroids and comets. |
| rotation | the action of rotating around an axis or center. |
| black hole | a region of space having a gravitational field so intense that no matter or radiation can escape. |
| gravity | the force that attracts a body toward the center of the earth, or toward any other physical body having mass. |
| asteroids | a small rock body orbiting the sun. these range in size from 600 miles across to dust particles. |