Transcript ppt
The Outer Planets Jupiter (5.20 au) Enormous size and mass make Jupiter undisputed giant of the solar system. • Galileo in 1995 orbited Jupiter and shot a probe into the atmosphere, radioed back data for an hour before it was crushed. • “Jovian” = giant Over 11X diameter and over 317X the mass of Earth, Jupiter is twice as massive as all the other planets combined! • Colorful Clouds and a Whirlpool of Wind – Light colored zones and dark colored bands created by jets of wind circulating in alternating directions. – 400 mph winds generated by convection currents, as Jupiter is still cooling from its formation. Jupiter’s Great Red Spot • Giant cloud, collosal eddy, observed for over 300 years, 25,000 miles long and 8,700 miles wide. • Similar high pressure swirls appear elsewhere on Jupiter, Saturn, and Neptune. • No one knows what sustains these systems. What do you think? Saturn (9.54 au) Spectacular ring system sets this second largest planet apart. • 2nd largest planet and 2nd largest mass. • 96% H, 3% He, less dense than water. • Rocky core is embedded in an outer core of water, methane, and ammonia. • Above the core is liquid hydrogen 21,000 km deep • Rocks, dust, and ice orbiting the planet form several large rings and thousands of narrow ringlets about 10 km thick • Has at least 30 known satellites. Its largest moon, Titan, is unique among moons for it has its own atmosphere. • Voyager 2 flyby in 1981 gave us close-up of rings and 1990 Hubble Telescope recorded enormous storms. Saturn’s Rings • Still not sure why Saturn or any planet has rings. • Maybe rings are the remains of a moon smashed by an asteroid. • More likely, the rings are made of particles that were unable to concentrate into a moon, because of the gravitational influence of the planet. Uranus (19.18 au) A puzzling blue-green world four times the size of Earth and 1.8 billion miles away. • Most of our knowledge of Uranus is from Voyager 2 which sped by in 1986. • A planet on its side: Since its rotation is nearly parallel with orbit about the sun, each pole spends 42 years in darkness and 42 years in light. • Beneath the Blue-Green Clouds: – A small rocky core is surrounded by thick layer of ice and rock and an outer layer of H and He. – Methane and ammonia condense into clouds at high altitudes. Methane gives Uranus its blue-green color. A narrow ring system of orbiting rock and ice was detetected by astronomers in 1977 and confirmed by Voyager 2 in 1986. Neptune (30.06 au) Smallest and most distant of the gas giants, 30,800 miles away. • Voyager 2 reached the 8th planet on Aug 25, 1989 revealing a blue disk with dark bands and white clouds. • Early in the 19C, unexplained perturbations were observed for Uranus. This led to the eventual finding of Neptune by astronomers in Germany and England. • Like Jupiter and Saturn, it emits twice as much heat as it receives from Sun. • Atmosphere mainly H and He; like Uranus, Neptune’s bluish color caused by clouds of methane. Neptune: Dim rings, violent storms, and an intriguing moon • 4 known rings, faintly detected; little known • Oval shaped high-pressure region 6,000 mi long with supersonic winds detected by Voyager 2. • Of 8 satellites, Triton is largest, a bit larger than Pluto; has numerous impact craters, curious pits, and volcanoes that release nitrogen, not lava. Pluto (39.44 au) Pluto is a tiny, cold rocky world with a tilted & very eccentric orbit. • • • • • • 248 years per revolution about sun 2.8 billion mi away at closest approach Only planet not visited by spacecraft Smallest planet, (< 1,430 mi diameter) smaller than Moon Rock-Ice composition similar to Triton Pluto has close relationship to its single moon, Charon; the two bodies spiral around a shared center of gravity. • Both may be captured objects that wandered in from the Kuiper Belt. • Amateur astronomer Clyde Tombaugh discovered Pluto in 1929. Courtesy Lowell Observatory The discovery photos for Pluto reveal the shift of one point of light between January 23, 1930 (left), and January 29, 1930 (right). The white arrows point to Pluto. Bodes Law, a fun math puzzle 0 +4 .4 3 6 12 24 48 96 .7 1.0 1.6 2.8 5.2 10.0 192 19.6 Bodes Law, a fun math puzzle 0 3 6 +4 .4 .7 1.0 Me V E 12 24 1.6 2.8 Ma Ast 48 96 192 5.2 Jup 10.0 19.6 Sat Uranus Distance of each planet from the sun in Astronomical Units (AU) 1 AU = 93 million miles, the ave distance to the Sun Comets “Dirty snowball” of water, ice and dust orbits the sun • Comets feature a head (coma) at front, and a tail that faces away from the sun. • Tail forms when ice is heated from sun, melts, and spreads out as a dust-filled gas. • Particles in tail may cause a meteor shower on Earth if we pass through the tail. • Famous comets include Hale-Bopp, Halley, Hyakutake, and Shoemaker-Levy 9.