| A | B |
|---|
| galaxy | hugh system in the universe including millions of stars |
| solar system | group of planets and other bodies that revolve around the sun |
| orbit | elliptical path that a planet follows in revolving around the sun |
| revolution | for a planet, one complete trip around the sun |
| leap year | year with 366 days to account for the extra one-fourth day in Earth's revolution around the sun |
| axis | imaginary line that runs through the earth's center between the North and South Poles |
| solstice | day in June and December when the sun is directly overhead at the Tropic of Cancer or the Tropic of Capricorn, marking the beginning of summer or winter |
| equinox | day in March and September when the sun's rays are directly overhead at the Equator, making day and night of equal length |
