A gravitationally bound system consisting of a sun and the objects that orbit it.

All of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.

An object's spinning motion about its own axis.

A huge collection of gas, dust, and billions of stars and their solar systems held together by gravity.

A large region in the solar system past Neptune where Pluto and other dwarf planets orbit the Sun along with rocks, dust, and ice.

An attractive force between two masses by which a planet or other body draws objects toward its center.

A region in the solar system roughly located between the orbits of the planets Jupiter and Mars that contains millions of irregularly shaped pieces of rock (called asteroids) as well as ice and dust.

A regular, repeating path that one object in space takes around another one.

An astronomical body that orbits a star, is big enough to have enough gravity to force a spherical shape, and is big enough that its gravity has cleared away any objects of a similar size near its orbit.