A
the average distance between the Earth and the sun; approximately 150 million Kilometers (symbol, AU)
astronomical unit
one of the highly dense planets nearest to the sun: Mercury, Venus, Earth, and Mars.
terrestrial planet
a small, rocky object that orbits the sun; most asteroids are located in a band between the orbits of Mars and Jupiter.
asteroid
a large cloud of gas and dust in interstellar space; a region in space where stars are born or where stars explode at the end of their lives.
nebula
a planet that has a deep, massive atmosphere, such as Jupiter, Saturn, Uranus, or Neptune.
gas giant
a small body of ice, rock, and cosmic dust that follows an elliptical orbit around the sun that gives off gas and dust in the form of a tail as it passes close to the sun
comet
the cloud of gas and dust that formed our solar system.
solar nebula
an event in which the shadow of one celestial body falls on another
eclipse
a bright streak of light that results when a meteoroid burns up in Earth's atmosphere
meteor
the counterclockwise spin of the planet or moon as seen from above the planet's North Pole; rotation in the same direction as the sun's rotation
prograde rotation
the change in the sunlit area of one celestial body as seen from another celestial body
phase
a meteoroid that reaches Earth's surface without burning up completely
meteorite
the clockwise spin of a planet or moon as seen from above the planet's North Pole.
retrograde rotation
a natural or artificial body that revolves around a planet
satellite
a relatively small, rocky body that travels through space
meteoroid