outer+planets

Outer Solar System Unit 4


 * Orbiting between Mars and Jupiter are asteroids or minor planets - cosmic junk pile of leftovers
 * what was left after the formation of the solar system, numbered in the millions
 * numerous, yet their combined mass is less than that of our moon
 * the presence of Jupiter prevents these rocks from collecting into another planet
 * most are just tens or hundreds of feet across, while a few are small worlds of their own right
 * Most of the asteroids exist in an area called the ASTEROID BELT
 * the belt ranges from 2.1 to 3.3 AUs from the sun
 * on the inner edge of the belt is about 1/3 AU thick and these asteroids take about 3 years to complete their orbit
 * on the outer edge it is about 1 AU thick and these rocks take 6 years to orbit
 * while it is often pictured as dense, if you were standing on one you might never see a neighboring one up close
 * There are some asteroids that share Jupiter's orbit
 * half of them exist about 60 degrees ahead of Jupiter orbit
 * the rest occupy the area about 60 degrees behind Jupiter's orbit
 * called Trojan asteroids
 * about 1500 Trojan asteroids have been identified
 * bother groups are herded in their locations by a tug-o-war between Jupiter and the Sun
 * Asteroids are classified into several types
 * M type: made of nickel and iron common in middle of belt
 * C type: high levels of carbon make up 75% of known asteroids
 * S type: mostly made of silicate (stony) material - more common in the inner part of the belt
 * Asteroids
 * Apophis - nearly 900 feet wide, 25 million tons
 * headed towards the earth
 * Friday April 13, 2029 is the day Apophis will head towards the earth at about 28,000 miles per hour
 * it will have the energy equal to about 60,000 times that of the bombs dropped on Hiroshima and Nagasaki
 * If it passes close enough (18,000 miles) then the Earth could alter its orbit in such away that is could return 7 years later April 13, 2036 and hit the Earth
 * chances are not high on this
 * Beyond the asteroid belt is the Outer Solar System
 * It is a wide range from 5 AUs to just over 50 AUs
 * The planets occupying the region are not like those in the Inner Solar System
 * Two largest - Jupiter and Saturn - gas giants, fluid planets made up the super-compressed hydrogen and helium
 * Uranus and Neptune - ice giants with thick atmosphere surrounding slushy mantles of ice and rock
 * Pluto - tiny planet in a class of its own.

Jupiter
Discovering Jupiter Major Stories of Jupiter Satellites of Jupiter Io Europa
 * Largest of the planets in our solar system
 * Average distance from the sun is 5.2 AU
 * Mass = 317.8 times that of Earth
 * Composed primarily of hydrogen and helium in super-compressed liquid form
 * No surface as such but may have a solid core of rock and ice
 * Rotation period is rapid - 9.92 hours
 * has at least 63 moons, the most of any planet in our solar system
 * most of small fragments of rocks
 * biggest 4-called the Galilean moons
 * has power magnetic field that extends to the orbit of Saturn
 * While Jupiter has been seen with the naked eye since mankind observed the skies, close to observation was not possible until Galileo Galilei invented the telescope and made observations.
 * He discovered the 4 largest moons, which have been called the Galilean moons in his honor.
 * Giovanni Cassini measured Jupiter's rotation period in 1665.
 * Robert Hooke is credited with discovering the red spot in 1664, but may have been another red spot he found.
 * Great Red Spot was definitely drawn by the German scientist Heinrich Schwabe in 1831
 * further detailed discovery was not possible until very large telescopes were built and then the first unmanned missions to Jupiter in the 1970's.
 * Bulk of the data collected up close about Jupiter were collected by the Pioneer and Voyager missions of the 1970's.
 * 1994 - Comet Shoemaker-levy 9 impacts the surface of Jupiter
 * over a period of a week, 20 fragments of the comet are slammed into Jupiter
 * Fragments hi the side facing away from the earth
 * since Jupiter rotates so quickly, the effects were seen soon after the impacts.
 * all available telescopes were aimed to Jupiter to get as much data as possible
 * models of Jupiter were altered based on data collected from the event.
 * only 4 of the 63+ are large
 * these are called the Galilean moons
 * Io, Europa, Ganymede, and Callisto
 * most of the others are small rocks probably captured asteroids
 * One of the innermost moons
 * colorful, and the most volcanically active body in the solar system
 * volcanoes spew molten sulfur dioxide which freezes in the cold atmosphere
 * constantly wrenched by the gravitational pull of Jupiter.
 * The other of the innermost of the moons of Jupiter
 * surface covered with think layer of ice
 * under the ice is a vast ocean of liquid water
 * water is kept in liquid form by the heating caused by the frictional pull of Jupiter's gravity.

Ganymede
Callisto
 * largest of the a galilean moons and largest moon in the solar system
 * Diameter=3270 miles
 * larger than mercury
 * composed of silicate rock and liquid water,with a molten iron core
 * the most heavily cratered object in the solar system
 * furthest of the Galilean moons from Jupiter

SATURN

 * located roughly twice as far from the Sun as Jupiter, or 10 times as far as the Earth
 * Gas Giant, spining sphere of hydrogen and Helium
 * most famous for te rings(not unique,all 4 of the giant planets hav rings)
 * rinds are the most visible, composed of water ice, highly reflective,visible through a telescope
 * visible to the naked eye, appearing as a yellowish, relitivly bright "star"
 * has atleast 48 natural satellites
 * Titan is a moon of Satern with substantial atmosphere
 * about 9 times the diameter of the Earth
 * Saturn along with 3 of is satellites picture taken by the Voyeger 2 mission in 1981
 * Black dot is a shadow cast by the upper of the 3 moons, Tethys
 * the other 2 moons are Dione and Rhea
 * Atmosphere is about 100 miles of ammonia ice, ammoninm hydrosulfide ice, and water ice or vapor
 * under that is the outer mantle of liquid hydrogen (from intense pressure)
 * Inner mantle is liquid metallic hydrogen
 * Core is possibly a rocky inner core and outer shell of ice
 * Largest moon is Titan, 2nd only to Jupiters Ganymede in size of moons in the Solar System
 * Only moon with substantial atmosphere
 * larger then Mercury or pluto
 * atmosphere is possibly like the conditions that existed on earth before oxygen was produced and released into atmosphere

Saturn's Titan

 * Surface temp of only about 94 Kelvin
 * probably the only place in the solar system that a person would freeze to death walking around on the surface wearing the same suits that the Apollo astronauts wore on the moon
 * this would be due to the atmosphere
 * the atmosphere would allow the heat to be drawn from the space suit, whereas a lack of atmosphere would not draw the heat out of the suit.
 * In 2005, the Cassin orbiter launched the lander Huygens, which landed on the surface of Titan and took pictures
 * pictures taken from 8km above the surface showed "river" channels
 * cause of the channels are not liquid water flowing, but liquid methane
 * **__titan is the only known body in our solar system to have liquid on its surface (other than earth)__**

Uranus

 * Discovered in 1781
 * about 19 AU from the Sun
 * Orbits sun in about 84 earth years
 * rotational axis is at 98 degrees and is nearly orbital plane, facing the poles towards the sun for long periods of time
 * due to distance from the sun and a deep atmosphere thats holds heat quiet well, temperature differences are minimal
 * 27 known satellites
 * Blue color is due to methane's tendency to absorb red and reflect blue end of spectrum
 * although methane provides the color, the majority of the atmosphere is hydrogen and helium (same proportions as the sun)
 * prior to the Voyager 2 mission little was known but many theories existed about the internal structure of Uranus
 * After Voyager 2 measured the distorted gravitational fields, it was determined that the best model was the Uranus has a small (3% of mass) rocky core surrounded by a thick layer of rock and ice in the formed of "mud"
 * There are 13 rings around Uranus, though they were only detected in 1977
 * the rings are very dark and reflect very little lightm suggesting that they might be made of carbon (methane under right conditions decomposes into carbon)