| A | B |
|---|
| black hole | an area of intense gravitational pull believed to be the site of a collapsed star; the final stage in the life cycle of massive stars |
| celestial | relating to the sky or the heavens |
| constellation | a pattern of stars, often named after a mythological figure |
| convex | curved or rounded, and thicker at the center and thinner along the edges |
| extraterrestial | not of our planet |
| light year | the distance a beam of light travels in one year, roughly 9.5 trillion km; the unit of measure used by astronomers to describe celestial distances |
| Milky Way | the galaxy in which our Solar System is located, medium in size and spiral in shape |
| myth | a traditional story, usually devised to explain a natural phenomenon |
| nebula | a cloud of dust and gas that exists in the space between stars |
| pulsar | a kind of star that sends out pulses of radio waves at regular intervals |
| red giant | the short stage in the life cycle of a star in which its energy production increases dramatically and it grows to an enormous size; after this growth spurt, the star begins to die |
| revolution | the orbital movement of a smaller celestial body around a larger one; the Earth makes one revolution around the Sun every 365 days |
| rise | to come up over the horizon into sight |
| rotation | the process of turning around a central axis; the Earth completes one rotation on its axis every twenty-four hours |
| star | a shining celestial body consisting of gases that produce by nuclear fusion |
| Stonehenge | an ancient astronomical observatory consisting of a ring of standing stones, built about 5,000 years ago in Salisbury, England |
| summer solstice | the day of the year on which the Sun rises highest in the sky; therefore also the longest day of the year |
| variable | in an algebraic equation, a factor whose value can be changed |
| white dwarf | the stage in the life cycle of an average star in which it collapses and begins to cool |
| Zodiac | the band of twelve galaxies in which the Sun, planets, and moons of our Solar System are always located |
| magnification | the enlargement of an image |
