Space

Asteroid

Pieces of rock found mostly in the asteroid belt between Mars and Jupiter; made up of minerals similar to those that formed the planets

Astronomical Unit

A unit of measure equal to 150 million km, which is the average distance from Earth to the Sun, and is used to measure the distances between the planets

Axis

The imaginary line that Earth spins around and whose tilt is responsible for Earth's seasons

Comet

An object in the solar system made up of ice, dust, and frozen gases that develops a tail of light when it swings close to the Sun

Eclipse

An event that happens when the moon passes between the Sun and Earth (Solar Eclipse) or Earth passes between the Sun and the Moon (Lunar Eclipse) producing a shadow

Galaxy

A group of starts, gas, and dust held together by gravity - for example, the Milky Way Galaxy, which contains 200 billion stars

Gravity

A pull that every objects exerts on every other object and that pulls all things toward Earth in the same way

Revolution

The movement of Earth in a regular, curved path around the Sun, which takes one year to complete

Rotation

The spinning of Earth on its imaginary axis, which occurs once every 24 hours and causes the day and night cycle

Satellite

A spacecraft that is launched into space to gather information and send it back to Earth

Solar System

The planets and numerous other objects, such as asteroids, that orbit the Sun

Star

A massive celestial body of gas that is held together by its own gravity; produces energy and gives off its own light

Tide

The changes in the level of ocean water during the course of a day - caused by the pull of gravity between Earth, the moon and the Sun

Planet

A celestial body larger than an asteroid or comet; produces NO light of its own, but is lit by a star in which it orbits

Universe

All space, matter, and energy, including Earth, the galaxies and everything in them, as a whole

Waning

The change in the Moon's appearance when it appears to be getting SMALLER from night to night

Waxing

The change in the Moon's appearance when it appears to be getting LARGER from night to night