| A | B |
|---|
| satellite | a natural or artificial body that revolves around a larger celestial body |
| moon | a celestial body that revolves around a body that is larger in mass; a natural satellite |
| mare | a large, dark area of basalt on the moon |
| crater | bowl-shaped depression that forms on the surface of an object when a falling body strikes the object's surface or when an explosion occurs |
| apogee | in the orbit of a satellite, the point at which the satellite is farthest from Earth |
| perigee | in the orbit of a satellite, the point at which the stellite is closest to Earth |
| eclipse | an event in which the shadow of one celestial body falls on another |
| solar eclipse | passing of the moon between Earth & the sun; during a solar eclipse, the shadow of the moon falls on Earth |
| lunar eclipse | the passing of the moon through Earth's shadow at full moon |
| phase | astronomy: change in the illuminated area of 1 celestial body as seen from another celestial body |
| Galilean moon | any one of the 4 largest satellites of Jupiter-Io, Europa, Ganymede, Callisto-discovered by Galileo in 1610 |
| asteroid | small, rocky object that orbits the sun; most are in a band between the orbits of Mars & Jupiter |
| comet | small body of rock, ice & cosmic dust that follows an elliptical orbit around the sun; gives off gas & dust in the form of a tail as it passes close to the sun |
| Oort cloud | spherical region that surrounds the solar system; extends from Kuiper Belt to almost halfway to the nearest star-contains billions of comets |
| Kuiper Belt | a region of the solar system that starts just beyond the orbit of Neptune-contains dwarf planets & other small bodies made if ice |
| meteoroid | a relatively small, rocky body that travels through space |
| meteor | a bright streak of light that results when a meteoroid burns up in Earth's atmosphere |
