| A | B |
|---|
| solstice | a point in Earth's orbit around the sun where daylight is either the longest or the shortest amount possible. |
| equinox | a point in Earth's orbit around the sun where nights and days are the same length. |
| lunar eclipse | a darkening of the moon when it passes through Earth's shadow. |
| tides | the rise and fall of water in the ocean and seas caused mainly by gravitational pull. |
| fusion | the combining of less massive elements to form more massive elements. |
| solar eclipse | an alignment of the sun, moon, and Earth where the moon blocks the sun from the Earth's view. |
| corona | a crown of growing gases around the sun that can be seen during a total solar eclipse. |
| sunspot | region on the sun of very strong magnetic field. |
| solar flares | powerful eruption of very hot gases from the sun. |
| auroras | the glow or display of lights in the skies near polar latitudes. |
| galaxy | a system of billions of stars, gases, and dust. |
| quasars | brilliant objects in space that may be the powerhouses of developing galaxies. |
| nebula | cloud of gas and dust in space. |
| red giant | a star that has swelled and glows with a red color. |
| supernova | the explosion of a star, releasing huge amounts of light. |
| black hole | an invisible object in space whose mass and gravitational force is so great that not even light can escape. |
| red shift | the change of light waves from retreating objects to the red end of the spectrum. |
| big bang theory | the idea that the universe started when matter exploded about 15 billion years ago. |
