| A | B |
|---|
| atmosphere | gas or air around a planet |
| axis | the imaginary line on which an object rotates |
| constellation | a group of stars forming a shape in the sky |
| equator | an imaginary circle around Earth that divides it into the Northern and Southern Hemispheres |
| galaxy | a large, independent system of stars (example: the Milky Way) |
| gravitation | a force of "attraction" between two objects |
| moon | a natural satellite that revolves around a planet |
| moon phase | the eight phases of the moon (in order: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, waning crescent) |
| planet | a large body in space that orbits a star and does not produce light of its own |
| solar system | a star and all the planets and other bodies that orbit it |
| star | a large, gaseous, self-luminous body held together by gravity and powered by thermonuclear reactions |
| Sun | the closest star to Earth and the center of our solar system |
| system | a set of objects, organisms, or different parts acting to form a whole |
| universe | the total sum of all matter and energy that exists |
