| A | B |
|---|
| Zenith | the point in the sky directly above the observer; the highest point |
| Supernova | a huge stellar explosion involving the destruction of a massive star in a sudden and tremendous brightening |
| Star | a self-luminous object that shines through the release of energy produced by nuclear reactions at its core |
| Solar System | the description given to the system dominated by the Sun and including the Planets, Minor Planets, Comets, planetary satellites and interplanetary debris that travel in orbits around the Sun |
| Sidereal Period | the time it takes one object to complete one orbit around another |
| satellite | a small object orbiting a larger one |
| rotate | to turn about a center point or axis |
| revolve | to cause to travel in a circle or orbit |
| Perigee | the point in its orbit around the Earth at which an object is closest to the Earth |
| orbit | the closed path of one object around another |
| Nova | a star, which suddenly flares up to many times its original brightness before fading again |
| Nebula | an interstellar cloud of gas and dust |
| nadir | that point on the celestial sphere directly opposite the zenith and directly below the observer(the lowest point) |
| Milky Way | the spiral galaxy containing our Sun; as seen from Earth, the constellation Sagittarius marks the direction to its center |
| meteorite | that part of a relatively large meteoroid that survives passage through the atmosphere and falls to the surface of a planet as a mass of metal or stone |
| meteor | the luminous phenomenom observed when a meteoroid is heated by its entry into the Earth's atmosphere |
| Light Year | the distance which a ray of light would travel in a year, about 6 trillion miles |
| Galaxy | a huge collection of stars, gas and dust measuring many light years across |
| eclipse | the hiding or blocking of one celestial object from another |
| constellation | a grouping of stars which many times form a shape or pattern |
| comet | a small, frozen mass of dust and gas revolving around the sun in a highly elliptical orbit |
| Black Hole | a region of space around a very small and extremely massive collapsed star within which the gravitational field is so intense that not even light can escape |
| axis | an imaginary straight line on which an object rotates |
| aurora | glows seen over the polar regions which occur when energized particles from the Sun react with particles from the Earth |
| asteroid | any of the thousands of small planets or MInor Planets, that orbit between Mars and Jupiter |
| apogee | the point in its orbit around the Earth at which an object is furthest from the Earth |
| Mercury | innermost planet, no satellites, no atmopshere |
| Venus | second planet from the Sun, thick atmosphere of carbon dioxide and sulfuric acid, no satellites |
| Earth | third rock from the Sun, atmosphere rich in oxygen and nitrogen, one natural satellite |
| Mars | fourth planet from the Sun, thin atmosphere of carbon dioxide, two moons |
| Jupiter | fifth planet from the sun, thick atmosphere of hydrogen, 16 known satellites |
| Saturn | sixth planet from the sun, similar to Jupiter, famous for its ring system |
| Uranus | seventh planet from the sun, atmosphere of methane, 6 known satellites |
| Neptune | eigth planet from the sun, similar to Uranus, tipped on its side, 8 known satellites |
| Pluto | outer most planet, small icy chunck of rock, no known atmosphere(too cold), one satellite(Charon) |
| Asteroid belt | group of rocks and debris found between the orbits of Mars and Jupiter |
