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Information about L23OutMo

Published on January 22, 2008

Author: Carmina

Source: authorstream.com

NATS 102, Sect. 12 – Fall 2006:  NATS 102, Sect. 12 – Fall 2006 Announcements Homework #4 available for download from the class web site DUE OCTOBER 20 NATS102 Star Party: Monday Oct 16 5:45 – 7:30pm Learn how to find the North Star, see Jupiter and Mercury, more *Hmk #3 Extra Credit: 5pts – we’ll take presence Oct 16, 7:30pm: Steward Observatory Public Evening Series Dr. Alfred McEwen – Early results from the HiRISE on Mars Reconnaissance Orbiter Steward Observatory, Rm N210 Celinda out of town: Oct 3-13 Paulo out of town: Oct 9-13 Reading: Chapter 16 of the text book Magic Trick!:  Magic Trick! Planets’ Moons:  Planets’ Moons A moon is a natural body (of any size) rotating around a planet, and usually much smaller than its planet Many moons are very small and may be asteroids captured by their planets There are almost 140 known moons in our Solar System! Jupiter has the most moons of any planet (63), followed by Saturn (33) Moons of Jupiter:  Moons of Jupiter Jupiter’s best known moons are the four large Galilean satellites: Io, Europa, Ganymede, Callisto Smaller, significant moons are Thebe, Amalthea, Adrastea, Metis, Himalia Jupiter has 63 confirmed satellites Jupiter's satellites are named for other figures in the life of Zeus Galilean Moons:  Galilean Moons *Earth Moon: diameter= 3,476 km density= 3340 kg/m3 Miniature Solar system Locked in 1:2:4 resonances Io:  Io Innermost of the four Galilean satellites (closest to Jupiter) Most volcanically active world in our Solar System Peppered with hundreds of volcanoes, high mountains, lava flows – no impact craters! Io’s Active Surface:  Io’s Active Surface Image sequence of two volcanic plumes 100 km (62 mi) high (Voyager 2) Eruptions at Tvashtar Catena (Feb. 2000) Telegonus Mensa, showing slumping, landslides, fracturing Mongibello Mons at sunset  7 km high (Nov. 1999) Hot lava! (Galileo Images) What fuels Io?:  What fuels Io? Accretional heat: Io is too small to have left over accretional heat Radioactive decay: not enough to generate the tremendous energy required to power the observed volcanic activity Tidal heating! Caused by the gravitational pull of Jupiter combined with the other Galilean satellites Galilean satellites are locked into “resonances” - Each time Ganymede orbits once, Europa orbits twice and Io orbits 4 times - The resulting tidal forces alternatively squeeze and stretch Io’s interior, generating enormous amounts of heat Io's surface can rise and fall by about 100 m (300 ft! The highest ocean tides on Earth only reach about 60 ft) Molten material and gases rise through fractures in the crust and erupt on the surface Europa:  Europa Second of the four Galilean satellites Bright, smoothest surface of the Galilean satellites The rock layer of Europa is surrounded by a shell of water (ice/liquid), and an icy crust Europa’s surface:  Europa’s surface Few craters… Europa’s complex surface (Galileo image) Ridges Mountains “Chaos” Pwyll Grainne “Chaos regions”: area that have been broken apart and "rafted" into new positions (similar to the disruption of pack-ice on polar seas during spring thaws on Earth) Ganymede:  Ganymede Surface is characterized by light and dark regions; bright regions appears younger than the dark, cratered areas They may represent crustal plates, similar to Earth’s plates It is heavily cratered especially in the dark regions implying an ancient origin of the surface Largest moon of the Solar System (larger than Mercury!) Ganymede:  Ganymede Khensu crater: dark-floored crater, 13 km in diameter “Nippur Sulcus”: younger, bright region overimposed on an older, darker region Ganymede’s dark region (Galileo+Voyager) A string of craters, similar to SL9 impact on Jupiter Callisto:  Callisto Second largest moon of Jupiter; about the size of Mercury Most heavily cratered satellite in the Solar System; ancient surface, 4 billion years No large mountains Callisto:  Callisto Chain of craters 620 km long, probably formed by a disrupted comet, like Shoemaker-Levy 9 (the largest crater is 40 km) Valhalla impact structure: bright central region is 600 km in diameter; concentric rings extend to 3000 km Surfaces of Galilean Satellites:  Surfaces of Galilean Satellites Very active surface No ice (too hot) No craters Io Europa Ganymede Callisto Active surface Ice shell (no rocks) Few craters “Plates” of different age Many craters Ancient surface Heavily cratered Slide16:  Minor Moons of Jupiter Metis & Adrastea - Small (40 & 20 km) and irregular, they are in almost identical orbits - They orbit Jupiter in 7 hours! Amalthea - Irregular in shape, 262 x134 km (163x83 mi), orbits Jupiter in 12 hours - Reddest object in the solar system, maybe due to sulfur emitted by Io and deposited on its surface Thebe - Irregular in shape: 110 x 90 km (68 x 56 mi) - Orbits Jupiter in 16 hours Himalia - Unusual angled orbit (probably a captured asteroid), about 170 km in size Moons of Saturn:  Moons of Saturn Titan is Saturn's largest moon Mimas has an enormous crater – probably caused by the impact of a large body Enceladus has a very bright, active surface; it may have active water volcanoes Tethys has a canyon running three-quarters of the way around its surface; it may once have been split almost in half Dione and Rhea have wispy white markings on one side Hyperion is oddly shaped and the length of its day is constantly changing Iapetus is half bright and half dark Titan:  Titan Saturn’s largest moon, with a thick, “smoggy” atmosphere about 4 times denser than Earth’s atmosphere Atmosphere is mainly nitrogen (N2) with few percent of argon (Ar) and methane (CH4) Cold surface, 94K (-240ºF) Huygens probe showed evidence of (past) fluvial processes Radar Images (2006): Methane lakes! Young surface, few craters so far Cassini Mission Moons of Uranus:  Moons of Uranus Most of the moons appear to be captured asteroids based to their size and orbit Titania, with a radius of 789 km, is the largest of Uranus moons; it has a large trench and few large impact craters Miranda and Ariel seem to have had violent pasts, and show huge canyons as deep as 20 km All the moons are made of ice and rock, with densities less than 2000 kg/m3 Titania Miranda Moons of Neptune:  Moons of Neptune Neptune has three main moons Nereid, Proteus and Triton plus five smaller moons; Triton and Proteus orbit close to Neptune, Nereid is in a distant orbit Nereid is the Solar System object with the most eccentric orbit Triton - Only moon in our Solar System in a retrograde orbit (orbiting in the direction opposite to Neptune’s rotation) - Coldest recorded object in our Solar System, with a surface temperature of 38K (-391ºF)! - Density of 2,066 kg/m3  contains more rock in its interior than the satellites of Saturn and Uranus - It has active geyser-like eruptions spewing nitrogen gas and dark dust particles several kilometers high Satellites of Giant Planets:  Satellites of Giant Planets Moons of the outer planets are ½ rock and ½ ice; only Io and Europa appear to also have an iron core Most moons display heavily cratered terrains (old surfaces), with the exceptions of Io, Europa, Triton and Titan Ganymede is the largest Satellite in our solar System, followed closely by Titan – both are bigger than Mercury! No craters have yet been found on Io Europa appears to have a deep ocean beneath its icy crust (Ganymede may have an ocean too!) Titan supports an atmosphere second only to Venus’ (considering bodies with proper surfaces), which is rich with organics, and whose origin is unknown Triton is the coldest recorded object in the Solar System with a surface temperature of 38K (-391°F) Pluto:  It has a large satellite, Charon, that is 1/2 Pluto’s size with a mass about 1/7 Pluto’s Pluto’s density is 1800-2100 kg/m3, Charon’s density is lower, 1200-1300 kg/m3 Surface could be as cold as 33K (-400ºF) but we have no measurements Pluto Dwarf Planet, located at the inner edge of the Kuiper Belt Composition: 50% to 75% rock mixed with ices Hubble Space Telescope (1994) Pluto Charon Pluto orbits the Sun in 248.5 years and rotates on its axis in -6.4 days Charon’s orbit is gravitationally locked with Pluto: 6.4 days (same as Pluto rotation) Eris, a.k.a. UB313:  Eris, a.k.a. UB313 Dwarf Planet, located in the Kuiper Belt Discovered in 2005, it caused a crisis of definitions in the astronomical community Named after the Greek goddess of discord and strife… Radius is estimated at 2400 km (largest object detected in the Solar System since the discovery of Neptune in 1846) It has a moon named Dysnomia, estimated to be about 1/8 of Eris’ size 3 images (over 3 hours), Oct. 2003 Keck Telescope Image

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