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Science Ch 5
| Term | Definition |
|---|---|
| planets | Any large body orbiting any star “wanderer” |
| perihelion | The point in a planet’s orbit at which a it is nearest to the sun |
| aphelion | The point in a planet’s orbit at which a it is furthest from the sun |
| Astronomical unit (a.u.) | The earth’s average distance to the sun = 1a.u. |
| mass | A measure of the amount of matter something contains |
| weight | The force of gravity exerted on an object |
| Surface gravity | The downward pull the planet exerts on objects at its surface |
| Inferior Planets | Planets closer to the sun than earth; mercury and Venus |
| Phase | (of a planet): the amount and shape of the planet’s illuminated surface that is visible from the earth. |
| transits | A planet passes directly between the earth and the sun so that we see its dark silhouette against the sun’s bright disk |
| Superior Planets | Planets whose orbits are further from the sun than earth’s orbit |
| Retrograde motion | The planet appears to move backward compared to the background stars |
| Terrestrial planets | “Earthlike”, Mercury, Venus, Mars |
| Jovian | Jupiterlike planets |
| Gas giants | One of the large, gaseous planets |
| Mercury | the fastest revolving planet |
| Kepler | developed three laws of planetary motion |
| Jupiter | the largest planet in our solar system |
| Mars | the red planet |
| ellipse | shape of planet's orbit |
| albedo | a planet's reflectivity |
| SETI | the program for identifying radio transmissions from intelligent alien races |