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the 3rd planet from the sun


any natural satellite of a planet


the natural satellite of the Earth


(physics) the force of attraction between all masses in the universe


any celestial body orbiting around a planet or star

artificial satellite

man-made equipment that orbits around the earth or the moon


Take 24 hours to revolve around Earth and always above same point on Earth's surface - most communication satellites are in this orbit

polar orbit

orbit that allows a satellite to travel around the earth, from pole to pole, in a short time to provide broad photo coverage of the planet

low earth orbit

an orbit located a few hundred kilometers above the earth's surface

orbital period

the time required for a body to complete a single orbit

orbital radius

distance from a satellite to the center of the object it is orbiting

orbital speed

the speed at which a planet is traveling in its orbit


a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit

Solar System

sun, planets, and all the other objects that revolve around the sun

Milky Way

the name of our galaxy, a spiral galaxy that contains about 400 billion stars


a collection of star systems


a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior



gravitational force

the force of attraction between all masses in the universe


everything that exists, including the sun, stars, all the planets, and outer space

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