| A | B |
|---|
| solar system | The sun and all the planets and other objects its gravity holds in orbit around it. |
| planet | Astronomical body that orbits the sun, with enough mass to form a spherical shape with enough gravity to clear the region of its orbit of smaller objects other than moons. |
| geocentric theory | Ancient solar system model with earth at its center and sun/ planets orbiting the earth in perfectly circular paths. |
| heliocentric theory | Solar system model placing sun at its center, with earth/ planets orbiting it. |
| orbit | Regular, elliptical path one astronomical body takes around another. |
| ellipse | The orbiting of a planet around the sun with the sun at one focus. |
| dwarf planet | Astronomical body that orbits the sun and not another object, having enough mass to be rigid and nearly spherical. |
| moon | A natural satellite of a planet. |
| small solar system body (SSSB) | Astronomical object that's not a planet or dwarf planet: moons, asteroids, comets and meteoroids. |
| terrestrial planet | Planet about the same size and density as the earth: Mercury, Venus, Earth or Mars. |
| Jovian planet | Planet similar in size and composition to Jupiter. |
| asteroid | Rocky object in orbit around the sun. |
| comet | Astronomical object in orbit around the sun made of rock and different kinds of ices meeting IAU definition of small solar system body. |
| meteoroid | Rocky object in orbit around the sun. |
| meteor | Meteoroid that falls through earth's atmosphere, heating up until it glows. "shooting star" |
| meteorite | Large meteor surviving fall through the atmosphere and hit the ground. |
