Unit 5: Solar System

2. rock and iron objects that orbit the Sun, much smaller than a planet. Millions are found between Mars and Jupiter, in the Asteroid Belt.
7. the turning of an object on its axis, in spinning motion; the Earth makes a full turn on its axis once every 24 hours (1 day).
8. a group of planets, moons, comets, asteroids, dust, gas and other objects that are bound by gravity and orbit a star (the Sun)
10. planets closest to the Sun, they are located between the Sun and the Asteroid Belt; Mercury, Venus, Earth, and Mars. Inner planets are dense and rocky, have a smaller diameter than the outer planets, and have thin atmospheres and few moons
11. the movement of one object around another; the Earth revolves around the Sun once a year; moons revolve around their planets.

1. ALL of space and everything in it, including stars, planets, solar systems, galaxies; contains more than a trillion galaxies
2. an imaginary line that goes through the center of an object; Earth’s axis passes through the North Pole, the center of the Earth, and the South Pole.
3. a large body in space, made of gas or rocks, that orbits a star and does not produce its own energy (heat and light)
4. the curved path of an object around a star, a planet or a moon
5. a large object in space that is made of gas and produces its own energy (heat and light)
6. a chunk of frozen gases, rock, ice, and dust. They have long orbits around the Sun and they have a tail that always points away from the Sun
9. a group made up of billions of stars, objects that orbit those stars, gas, and dust, held together by gravity.