Astr 100 Exam 2

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 temperatures very high and nighttime temperatures very low * VENUS= surface covered by thick sulfuric acid clouds (yellow-orange color) * Closest to earth in size * No moon * Hotter than mercury * High temps due to CO2 atmosphere * Venus’ clouds hide its surface from study visible light; to see Venus’ surface we use radio waves * Many volcanoes, but little craters * EARTH= water planet * Only planet where seasons, atmosphere, life come together * MOON * Largest moon of the terrestrial planets * Heavily cratered surface, but with large, dark plains called mare that have fewer craters * MARS= the red planet * Water-ice clouds, polar ice, and volcanoes * Moons are small captured asteroids (Phobos and Deimos) * 50% Earth’s radius * 10% earth’s mass * Atmosphere 1% thickness of earth, mostly CO2 * Similar surface to earth * Similar rotation period to earth * Farther from sun makes surface very cold * Largest volcano (Olympus Mons) * JUPITER= King of the Planets * over 300 times the mass of the Earth * mass is more than twice that of all the other planets combined * The planet's swirling cloud stripes are punctuated by massive storms such as the Great Red Spot * Dozens of moons * SATURN= Lord of the Rings * Rings made of ice, rock, and dust * Massive ball of hydrogen and helium * URANUS * more methane in its mainly hydrogen and helium atmosphere than Jupiter or Saturn (blue tint) * equator perpendicular to orbit (rotates on its side) from collision with earth like object * NEPTUNE * Dark, cold and whipped by supersonic winds * twin in size and mass to Uranus * methane atmosphere (blue tint) * More than 30 times as far from the sun as Earth (165 Earth years to orbit sun) * DWARF PLANETS * Much smaller than terrestrial planets and moon * Beyond Neptune = Pluto, Eris, Makemake, Haumea (mostly ices) * Between Mars and Jupiter= Ceres (rock) * ASTEROIDS * Rocky, airless worlds that orbit the sun * Too small to be called planets * Asteroid Belt is between Jupiter and Mars * Ceres is largest * COMETS * dirty snowballs of ices, rock, and dust * 3-10 km long * Most orbit beyond Neptune (then frozen) * When near the sun, heats up and tail is millions of km long * KUPLIER BELT * roughly a thousand small, dark, icy bodies orbiting in the outer fringes of the solar system beyond Neptune * SOLAR SYSTEM MOONS * Over 160 * Jupiter & Saturn= 60 each, mostly small * Uranus & Neptune= 1-2 dozen each * Pluto= 4 moons * Eris= 1 moon * PLANET CHARACTERISTICS * Is in orbit around the sun * Has sufficient mass to assume nearly round shape * Has cleared the neighborhood around its orbit * DWARF CHARACTERISTICS * Is in orbit around the sun * Has sufficient mass to assume nearly round shapes

* CLUES TO HOW SOLAR SYSTEM FORMED * Solar system orbits and rotates in an orderly pattern * Orbit west to east (counter-clockwise) * Nearly same plane * Most rotate in same direction * Most moons orbit in same direction * Two major groups of planets * Asteroids and comets populate solar system * SOLAR NEBULAR THEORY * our solar system formed from a giant cloud of interstellar gas and dust * The Eagle Nebula is a called where stars are forming * Stars form from cold, dense clouds of gas and dust in interstellar space that collapse under the influence of their own gravity *