| A | B |
|---|
| astronomy | study of the universe |
| universe | everything the exists (including Earth, the planets, the stars, and all of space) |
| telescope | a device that collects light and magnifies distant images to make them look closer, larger, and brighter |
| rotation | one complete spin on an axis |
| standard time zone | a vertical belt, about 15 degrees wide longitude, in which all locations have the same time |
| international Date Line | the 180 degree of longitude (going west acros it adds a day and going east subtracts a day) |
| revolution | one complete trip around the Sun |
| visible light | light that you can see with your eyes |
| refracting telescope | uses lenses to gather light from a faraway object |
| reflecting telescope | visible light reflects off a series of two or more mirrors |
| invisible light | light that people cannot see |
| apparent path | the Sun appears rises in the east and sets in the west as a result of Earth's rotation |
| space shuttle | a reusable spacecraft |
| crater | bowl shaped depressions on the Moon's surface |
| phases of the Moon | the shape of the Moon we see in the night sky |
| lunar eclipse | when Earth blocks sunlight from reaching the Moon |
| solar eclipse | when Earth passes through the Moon's shadow |
| tide | the regular rise and fall of the water level along a shore |
| gravity | the force of attraction among all objects |
| maria | large, dark, flat surface areas on the moon |
| mare | means 'sea' in Latin |
| spring tide | high tides are higher than usual |
| neap tide | high tides are lower than usual |
| gravitational pull | between the Moon and Earth causes changes in the tides |
| planet | a large body that orbits a star |
| moon | an object that orbits a planet |
| solar system | the Sun and all the planets, moons, and other bodies traveling around it |
| inertia | the tendency of a movong object to stay in motion |
| asteroid | rocky or metallic objects that orbit the Sun |
| comet | a ball of ice and rock that orbits the Sun |
| meteoroid | a small rocky object that orbits the Sun in both the inner and outer regions of the solar system |
| meteor | a meteoroid that enters the Earth's atmosphere |
| meteorite | a meteoroid that strikes the Earth's surface |
| inner planets | planets closest to the Sun - Mercury, Venus, Earth, Mars |
| outer planets | larger planets beyond the asteroid belt - Jupiter, Saturn, Uranus, Neptune |
| gas giants | the outer planets with a small, metallic core and a thick atmosphere |
| star | a large, hot ball of gases, held together by gravity, that gives off its own light |
| constellation | a group of stars that appear to form a pattern |
| parallax | the apparent shift in an object's positin when viewed from two locations |
| light-year | the distance that light travels in one year |
| nebula | a huge cloud of gas and dust in space |
| supernova | an exploded star |
| black hole | is an object whose gravity is so strong that even light cannot excape from it |
| absolute magnitude | a star's actual brightness |
| apparent magnitude | how bright a star looks in the Earth's night sky |
| protostar | a young star |
| galaxy | a group of star clusters held together by gravity |
| Milky Way | the Earth's galaxy |
| spectrum | a band of colors made when white light is broken up |
| big bang | the expansion of the universe rapidly |
| background radiation | comes from all directions in space and is radiation left over from the beginning moments of the universe |
