| A | B |
|---|
| Galaxy | Huge system in the universe including millions of stars. |
| Solar system | Group of planets and other bodies that revolve around the sun. |
| Orbit | The path that a planet follows in revolving around the sun. |
| Revolution | One complete trip around the sun. |
| Leap year | A year with 366 days to account for the extra one-fourth day in Earth's revolution around the sun. |
| Axis | The horizontal (bottom) or vertical (side) line of measurement on a graph |
| Solstice | Day in June and December when the sun is directly overhead at the Tropic of Cancer or 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 or equal length. |
