U6 Earth's place in the Universe

Satellite

An object that orbits a planet. Any object that orbits around another object in space

Star

A ball of hot gas, primarily hydrogen and helium, that undergoes nuclear fusion

Planet

An object that orbits a star, is a large enough to have become rounded by its own gravity, and has cleared the area of its orbit

Meteor

A streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere

Comet

A loose collection of ice and dust that orbits the sun, typically in a long, narrow orbit

Heliocentric

Term describing a model of the solar system in which Earth and the other planets revolve around the sun.

Eclipse

The partial or total blocking of one object in space by another

Constellation

A pattern or grouping of stars that suggest the outline of a figure or object

Axis

An imaginary line that passes through a planet’s center and its north and south poles, about which the planets rotates

Rotation

The spinning motion of a planet on its axis

Revolution

The movement of an object around another object

Solstice

Either of the two days of the year on which the sun reaches its greatest distance from the equator

Equinox

Either of the two days of the year on which neither hemisphere is tilted toward or away from the sun

Inertia

The tendency of an object to resist a change in motion

Law of Universal Gravitation

The scientific law that states that every object in the universe attracts every other object

Umbra

The darkest part of a shadow

Penumbra

The part of a shadow surrounding the darkest part

Gravity

The attractive force between objects; the force that moves objects downhill

Spring Tide

The tide with the greatest difference between consecutive low and high tides

Neap Tide

The tide with the least difference between consecutive low and high tides