Astro 1

75% hydrogen, 25% helium, less than 1% oxygen and several other elements

mercury, venus, earth, mars, jupiter, saturn, Uranus, Neptune, Pluto.

Pluto, Eris, Ceres, Haumea, Makemake

Spherical, at least 500 miles across, smaller than mercury, don't have to have enough gravity to collect other objects and clear out their orbital area.

167 plus moons

Mercury and Venus have no moons.

Mostly rock or metal, they formed closer to the Sun than the comets did.

The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets.

Mostly ice and rock, they formed much farther from the sun than the asteroids did.

Comets are found in two main regions of the solar system: the Kuiper Belt and the Oort Cloud. There are two types of comets: short-period comets and long-period comets. Short-period comets - comets that frequently return to the inner solar system - probably come from the Kuiper Belt beyond the orbit of Neptune.

short-period comets and long period comets

The Oort Cloud is an extended shell of icy objects that exist in the outermost reaches of the solar system.

Kuiper belt, is a region of the Solar System beyond the planets, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun.

Is made by nuclear fusion reaction in its core( for this to happen, a star must be born with at least 1/10 the mass of the sun, or about 100 times the mass of Jupiter. )

Must be at least as large as Mercury.

a moon is any natural object, big or small, that orbits a planet and has an accurately known orbit.