Solar System Vocab

asteroid

an irregularly shaped rock that orbits the Sun.

comet

a space object made of ice and dust that orbits a star and develops a long, bright tail as it nears its star.

core

the center of an object

crater

a hole in the ground caused by the impact of an object from space.

dwarf planet

a nearly round object that orbits a star, is smaller than a planet, and is not a satellite of another object.

gas giant

a large planet that is mainly made up of gases.

gravity

the force that pulls all objects toward each other.

moon

a huge ball of rock that travels around a planet; a natural satellite

orbit

to revolve around another object.

planet

large bodies, natural satellites, that orbit the Sun, a star.

satellite

a natural or human-made object that orbits Earth or another object in space.

solar system

a group of objects in space that orbit a star.

star

a body in outer space, made of hot gases, that shines in the night sky.

terrestrial

like Earth; describes planets that are rocky and Earthlike in size.

asteroid belt

the area in space between Mars and Jupiter where most asteroids orbit.

atmosphere

a layer of gases surrounding a planet, star, or moon.

gas

a substance with no fixed volume or shape that can expand freely.

helium

the second lightest chemical element; often a gas.

hydrogen

the lightest chemical element; often a gas.

mass

the measure of the amount of matter in an object.

methane

a colorless, odorless, flammable gas commonly called "natural gas".

oxygen

a gas that has no color, taste, or smell, and which people need to live.