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Unit 3
| Term | Definition |
|---|---|
| Solar system | The sun and all of the plants and other that travel around it |
| Heliocentric | Sun-centered |
| Geocentric | Describe something that uses Earth as the reference point |
| Parallax | An apparent shift in the position of an object when viewed from different locations |
| Gravity | A force of attraction between objects that is due to their masses |
| Orbit | The path that a body follows as it travels around another body in space |
| Aphelion | In the orbit of a planet or other body in the solar system, the point that is farthest from the sun |
| Perihelion | The point in the orbit of a planet at which the planet is closest to the sun |
| Centripetal force | The inward force required to keep particle or an object moving in circular path |
| Solar Nebula | A rotating cloud of gas and dust from which the sun and planets formed |
| Planetesimal | A small body from which a planet originted in the early stages of development of the solar system |
| Nuclear Fusion | The process by which nuclei of small atoms combine to form a new, more massive nucleus; the process releases energy |
| Sunspot | A dark area of the photosphere of the sun that is cooler than the surrounding areas and that has a strong magnetic field |
| Solar flare | An explosive release of energy that comes from the sun and that is associated with magnetic disturbances on the sun's surface |
| Prominence | A loop of relatively cool, incandescent gas that extends above the photosphere and above the sun's edge as seen from Earth |
| Terrestrial Planet | One of the highly dense planets nearest to the sun; Mercury, Venus, Mars, and Earth |
| Astronomical Unit | The average distance between Earth and the sun; approximately 150 million kilometers symbol, AU |
| Gas giant | A planet that has a deep, massive atmosphere, such as Jupiter, Saturn, Uranus, or Neptune |
| Planetary ring | A disk of matter that encircles a planet and consists of numerous particles in orbit, ranging in size from dust grains up to objects tens of meters across |
| Dwarf Planet | A celestial body that orbits the sun, is round because of its own gravity,but has not cleared its orbital path |
| 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 |
| Kuiper Belt object | One of the hundreds or thousands of minor planet-sized objects that orbit the sun in a flat belt beyonds Neptunes orbit |
| Comet | A small body that give off gas and dust as it passes close to the sun; a typical comet moves in an elliptical orbit around the sun and is made of dust and frozen gases |
| Oort Cloud | A spherical region that surrounds the solar system, that extends from the Kuiper Belt to almost halfway to the nearest star, and that contains billions of comets |
| Asteroid | A small, rocky object that orbits the sun; most asteriods are located in a band between the orbits of Mars and Jupiter |
| Meteoroid | A relatively small,rocky body that travels through space |
| Meteor | A bright streak of light that results when a meteoroid burns up in Earths atmosphere |
| Meteorite | A meteoroid that reaches Earths surface without burning up completely |