Question | Answer |
planets | greeks called wanderers |
perihelion | when a planet is closest to the sun |
aphelion | when a planet is farthest from the sun |
astronomical unit/ ua | the earth's average distance from the sun |
albedo | indicates a planets reflective ability |
mass | a measure of the amount of matter the planet contains |
inferior planets | the planets whose orbits are between the earths orbit and the sun |
phases | the amount and shape of the planet's illuminated surface that is visible from the earth |
transits | when 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 that are further from the sun than the earth's orbit,move slower than the earth |
retrograde motion | when the earth passes a superior planet and the planet appears to move backwards compared to the backward stars |
terrestrial planets | planets that are the earths size or smaller have have about the same density as the earth |
jovian | also called Jupiterlike stars |
gas giants | planets that are mostly gaseous |
phobos and deimos | Mars' two moons named after the attendants of the Greek god of war |
galilean moons | moons that Galileo discovered |
great red spot | a feature on jupiter that is a reddish-colored, rotating, oval shaped area that astronomers have been trying to explain for centuries |
ganymede | a galilean moon that is larger than Mercury and Pluto |
Cassini's Division | a group of rings that surround Saturn that appears to be completely empty from earth |
Uranus | discovered in 1781 by William Herschel |
Urbain Jean Joseph Leverrier and John Couch Adams | two mathematicians that made independent calcuations about where a new planet would have to be to affect Uranus's orbit |
Johann Gottfried Galle | found a new planet in 1846 less than 1˚ from the position that Leverrier had calculated |
Percival Lowell | a wealthy american businessman and astronomer that built his own observatory in order to search for a unknown planet and calculated where another planet should be and got pictures of "planet X" |
Clyde Tombaugh | found the exclusive "planet X" |
Pluto | earlier called planet X |
surface gravity | the downward pull the plane exerts on objects at its surface |