Space Term Glossary

Asteroid (also called planetoid) - A medium-sized rocky object that orbits the Sun. It's smaller than a planet but larger than a meteoroid. Also, any number of small bodies that revolve around the Sun.

Atmosphere - The air all around Earth.

Black Hole - An object with gravity strong enough to suck anything into it, even light.

Celestial Bodies - Natural objects visible in the sky - planets, stars, meteoroids, etc.

Comet - A giant snowball of ice and dust that revolves around the Sun. When it gets near the Sun, ice melts and looks like a tail. Haley's comet is probably the most famous comet.

Constellation - A group of stars that make a shape (they look like connect-the-dots) - usually named after mythological characters, people, animals and things.

Eclipse - This is when one celestial body cuts off the light of another - like when the moon covers the Sun for a brief moment.

Galaxy - A large group of stars. Our galaxy (called the Milky Way) includes the Sun.

Gravity - The natural force of attraction that pulls objects together - this is also what keeps our feet on the ground.

Great Red Spot - A huge colorful swirl of gases that spin counterclockwise on Jupiter.

Light Year - The distance light travels in a vacuum in one year (about 9.5 trillion km/6 trillion miles.)

Meteor (also a shooting star or a falling star) - A bright streak of light in the sky caused by a meteoroid or a small icy particle as it burns up entering Earth's atmosphere. Very large, bright ones are called fireballs and bolides.

Meteorite - A part of a meteoroid found on Earth.

Meteoroid - A small rock in space.

Orbit - The path that an object moves around a second object or point. For example, Earth orbits the Sun.

Planet - An object bigger than an asteroid orbiting a star. Our solar system has nine planets.

Satellite - A body that revolves around a larger body. The moon is a satellite of Earth. High-tech manmade satellites orbit Earth and the Sun, transmitting pictures, TV channels and phone signals.

Shooting Star - See meteor.

Solar System - The Sun, the nine planets and any other celestial bodies that orbit the Sun.

Solar Wind - A thin flow of energetic and gas charged particles that stream from the Sun. These blow throughout the solar system at speeds of hundreds of kilometers per second.

Speed of Light - 299,792,458 meters/second (186,000 miles/second.) Einstein's Theory of Relativity says that nothing can go faster than the speed of light. Of course, the crew on the Starship Enterprise knows better.

Star - Any celestial body that is visible at night (because it's brightly lit) from Earth at night.

Universe - All the matter and energy out there - this includes the Earth, galaxies, solar systems, you, your favorite pop star and everything else.

White Dwarf - The 'remains' of a star after it has collapsed. It is white looking (because it's so hot) and is extremely dense.

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