Chapter 17

Made of the Sun, its eight planets, dwarf planets, moons, asteroids, and comets

The path that the planets follow around the Sun, or Moon around the Earth

One full orbit

a few hours longer than 365 days (one year)

28 days (one month)

Keeps planets in their orbits around the Sun and it keeps the Moon orbiting Earth

An imaginary center line that the Earth spins or rotates on.

One whole spin of an object on its axis; Earth completes one rotation or day in about 24 hr.

its axis always points in the same direction in space.

helps prevent Earth from overheating & insulates the surface to keep the planet warm.

Determined by the tilt of the Earth toward the Sun

Just Sucked Up Noodles

Determined by distance from the Sun

Used to measure distance in space (1 AU is distance between Earth & the Sun)

Spacecrafts that gather data without a crew; used to explore other planets

Mercury, Venus, Earth, and Mars

Closest to Earth; has a thick, cloudy atmosphere of poisonous gases; clouds trap Sun's heat

Scientists think Mercury's core is 3/4 iron; has almost no atmosphere;temps vary greatly

Jupiter, Saturn, Uranus, and Neptune; made mostly of hydrogen, helium, & other gases

Where Kuiper is located; contains thousands of icy, rocky objects known  as KBOs