| A | B |
|---|
| Galilean Moons | The four largest of Jupiter's 63 moons. |
| Greenhouse Effect | Gasses can trap heat within its confines. This process explains how an atmosphere, made of gasses, can keep a planet warm. |
| Impact Crater | This is the after math of a collision when a huge object hits another and leaves a depression. |
| Meteor | When a rocky particle hits the Earth's atmosphere it is burned up by the friction due to atmospheric gases causing a streak of light. |
| Meteorite | If a rocky particle survives the atmospheric gases and hits a planet it is then called this. |
| Meteoroid | A small rocky particle that moves through space. |
| Terrestrial Planet | The four inner rocky planets that are closest to the Sun. |
| Asteroid | An item that is simply a rocky object which orbits the sun. |
| Astronomical Unit | A distance measurement used specifically for our solar system; 1 AU is equal to the distance from the Sun to the Earth. |
| Comet | A small rocky and icy object that orbits the Sun. |
| Star | A large sphere of hydrogen gas, held together by gravity, that is hot enough for nuclear reactions to occur in its core. |
| Period of Revolution | The time it takes an object to travel once around the Sun. |
| Period of Rotation | The time it takes an object to complete one turn on its axis. |
| Orbit | The path an object follows as it moves around another object. |
| Galaxy | a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction. |
| light year | The distance that light travels in one year |
| AU | astronomical unit (distance from the earth to the sun) |
| universe | All of space and everything in it |
| composition | the makeup of something |
| dwarf planets | a celestial object that does not clear its neighborhood; ceres, pluto, eris, makamake,haumea |
| Kuiper belt | A region of the solar system that is just beyond the orbit of Neptune and that contains small bodies made mostly of ice; a second asteroid belt |
| gas giants (Jovian planets) | The name given to the first four outer planets because they're mostly hydrogen and helium, have a thick gas and liquid layer covering a small solid core: Jupiter, Saturn, Uranus, and Neptune |
| Parsec (pc) | The distance to an object with a parallax angle; approximately equal to 3.26 light-years. |
