Astr 100 Exam 2

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Sun= cantaloupe
Earth = ball pen
Jupiter= finger tip
Pluto= dust

* Today we know Solar system has: 1 star, 8 planets, 5 dwarf planets, 139+ moons, countless small solar system bodies * A major lesson from all this is that the solar system is almost entirely made of nearly empty space * All planets orbit the sun in the same direction (counter-clockwise) * Most rotate in the same direction

* Venus rotates backward
* Uranus rotates on its side (equator perpendicular to equator) * nearly all the moons in the solar system, including Earth’s moon, orbit around their planets counterclockwise * mercury’s orbit is the least circular

* dwarf planets like Pluto have very eccentric orbits
* planet orbits lie on common plane (flat and disc shaped) * mercury tipped 7 degrees while no other planet inclined more than 3.4 degrees * dwarf planets like Pluto can be very inclined
* terrestial (inner) vs. jovian planets (outer)
* Closer to sun
* Smaller sizes and masses
* High densities
* Rock and metal vs. hydrogen and helium ices
* Solid surface vs. none
* Warmer surfaces vs. cold temps at cloud tops
* Few moons
* No rings

* SUN = hydrogen and helium
* Earth travels around the sun at an average distance of about 149,600,000 kilometers (92 million miles) * The sun's diameter is about 1.4 million km (864,000 miles), approximately 109 times Earth's diameter. * The Sun has 99.8% of the mass in the entire solar system * Its mass is roughly 2 X 1027 tons

* about 333,000 times as massive as Earth.
* MERCURY= barren, airless world
* Mercury has a heavily cratered surface.
* No moon
* 30% larger diameter than the Moon
* Orbits every 88 days
* Most eccentric orbit
* Rotates once per 59 days
* One day last 176 earth days or 2 mercury years
* Lack of an atmosphere and long days means daytime...
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