| A | B |
|---|
| asteroid | small solid objects made of iron, nickel, stone, or any combination of the three, which orbits the sun; are sometimes called minor planets or planetoids |
| comet | an icy object orbiting the Sun; has been described as a “dirty snowball” |
| dwarf planet | maintains a nearly round shape as planets do, but it cannot move other objects away from its orbital neighborhood. |
| elliptical | the shape (oval) of the planets’ orbits |
| geocentric theory | a scientific theory based on the idea that the earth is the center of the solar system (incorrect) |
| gravitational pull | the attraction that one object has for another object due to the invisible force of gravity |
| gravity | a mutual physical force attracting two bodies that have mass |
| heliocentric theory | a scientific theory based on the idea that the sun is the center of the solar system (correct) |
| meteor | when a meteoroid enters the Earth’s atmosphere and begins to burn, causing a streak of light in the sky; also known as a falling or shooting star |
| meteor shower | occurs when the Earth passes through a wave of meteoroids and a great number of meteors fall to the Earth |
| meteorite | when a meteor reaches the surface of the Earth |
| meteoroid | small bits of rock and dust that orbit the Sun |
| orbit | the curved path that a celestial body follows when revolving around another body |
| planet | a round ball of rock and/or gas that orbits a star |
| revolution | one complete orbit around another body |
| rotation | one spin of a planet on its axis; causes day and night |
| satellite | a body that revolves around a larger body; can be natural (i.e. moon) or artificial (i.e. man-made) |
| star | a ball of mostly hydrogen and helium gas that produces its own light through nuclear fusion |
