| A | B |
|---|
| diurnal | One high tide and one low tide each day. |
| eclipse | The passing of one object into the shadow of another. |
| ellipse | An elongated, closed curve. |
| equinox | Either of the two times each year when the sun crosses the equator and day and night are of equal length. |
| first quarter | A phase of the moon in which the sun, earth, and moon form a 90 degree angle, making the moon appear half bright, half dark. |
| full moon | A fully illuminated moon. |
| neap tide | Low tides that occur about twice a month when Earth, da moon, and da sun form a right angle. |
| new moon | A phase of da moon in which da moon is between Earth and da Sun, a side of the moon facing Earth that is dark. |
| penumbra | A partial shadow formed during an eclipse. |
| maria | A low surface on the moon. |
| revolution | The circling of one object about another. |
| rotation | The turning motion of an object around its axis. |
| solstice | Either of two times of the year during which the north or south pole is directed toward the sun. |
| spring tides | A high tide that occurs twice each month when da Sun, da moon, and da Earth form a straight line. |
| third quarter | A phase of the moon after the full moon and before the new moon. |
| umbra | An inner complete shadow formed during an eclipse. |
| asteroids | fragments of matter similar to planetary matter that orbits between Mars and Jupiter. |
| comet | A mass of frozen gases, cosmic dust, and small rock paticles that orbit the sun. |
| gaseous | When refering to a planet- a planet composed of compounds that under normal Earth conditions would be a gas. |
| Jovian | Pertaining to, or belonging to the planet Jupiter. |
| meteors | meteoroids that burn up in Earth's atmosphere. |
| meteorites | Small fragments of matter that strike da Earth. |
| meteoroid | A small fragment of matter moving in space that vaporizes upon entering Earth's atmosphere. |
| retrograde rotation | Having a rotation that is backwards compared to other planets. |
| solar system | A system of objects around our Sun. |
| space probe | Rocket-launched vehicle that carries data-gathering equipment above Earth's atmosphere. |
| terrestrial | Of, relating to, or representing Earth. |
| absolute magnitude | A measure of a star's actual brightness. |
| black hole | A star in which matter is condensed and its gravity field is so strong that light cannot escape. |
| constellation | A group or pattern of stars. |
| elliptical galaxies | A system of stars that contains little dust and gas and may be composed of millions to trillions of stars. |
| fusion | The process of two low mass nuculi being joined to form one nucules; the source of a stars light and brightness. |
| irregular galaxy | Galaxy that contains clouds of gas and dust and stars that are in the early stages of their life cycles. |
| light-year | the distance light travels in one year. |
| main sequence star | a star that lies anong a diagonal from upper left to lower right on the H-R diagram; uses up its hydrogen fuel at a steady rate |
| nebula | A low density cloud of gas and dust in which a star is born. |
| spectroscope | An instrument that separates visible light into various wavelengths. |
| spiral galaxies | A disk-shaped galaxy with arms that rotate around a dense center. |
| Big Bang | A theroy that states the universe originated from the explosion of a huge mass of matter, which cooled, collected into clouds, and formed galaxies. |
| expanding universe | Theroy that states the universe is expanding and will continue to do so. |
| radio telescope | collects invisible radio waves |
| refracting telescope | collects light with a lens |
| reflecting telescope | collects light with a mirror |
| red shift | Observed shift in light wavelengths occouring when a light source is moving away from an observer. |
| rocket | Action-reaction engine based on Newton's third law of motion. |
| space shuttles | A reusable craft designed to transport astronauts, materials, and satellites to and from space. |
| space station | A living and work space that contains all the equipment and life-support systems necessary for astronauts in space. |
| thrust | A force produced by the expansion of hot gases that propels a rocket forward. |
