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Misc SS Topics Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Cartoon of the Day “I was, I remember, I still remember when the first time I pointed the telescope at the sky and I saw Saturn with the rings. It was a beautiful image.” —Umberto Guidoni “The scientific theory I like best is that the rings of Saturn are composed entirely of lost airline luggage.” —Mark Russell Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Announcements • • • Midterm graded, will debrief Tuesday Have you selected your observing project yet? Any more makeups to schedule????? Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Last Class • • • LT Greenhouse Effect debrief Climate Change Small Solar System Bodies • • • • • Meteor/oid/ite Asteroids Comets Kuiper Belt Mars (not complete) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 This Class • • • A bit more mars Jovian Planets, Enceladus & Titan Dwarf Planets & Pluto Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 MARS CTD Surface of Mars False-Color Topographic Map from Mars Global Surveryor Olympus Mons Valles Marinaris Hellas Basin Argyre Basin Northern Lowlands Southern Highlands Astronomy 1 - Elementary Astronomy Impact Craters Rift Valleys Volcanos LA Mission College Levine F2015 Hemispheric Dichotomy • The N Hemisphere is very different from the S Hemisphere • • • Topography Crust thickness Resurfacing Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Craters on Mars NASA/HiRISE/Univ. of Arizona) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Vulcanism on Mars • • Shield Volcanos Olympus Mons • • Highest & Largest in Solar System! Tharsis Rise • • • Volcanic Bulge 10 km above mean radius Nearly as large as the US Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Valles Marinaris NASA JPL/ • • Great Rift Valley -- Tectonic • • Could reach from LA to NY 4x deeper than Grand Canyon There are larger rift valleys on Earth Astronomy 1 - Elementary Astronomy LA Mission College NASA Levine F2015 Mars Below the Surface NASA • • • • Solid core - Magnetic field gone when cooled Soft, thick mantle No active plate tectonics Crust ~30-150 km thick Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 What happened to the Water? (One explanation) • Mars is small • • It Cooled & Lost its magnetic field Solar wind sand blasted away the atmosphere • Lack of atmosphere allowed Solar UV radiation to penetrate to Mars’ surface • UV radiation dissociated H2O molecules • H lost to space, O reacted with Iron in the surface rock to form iron oxide (rust) • Mars is now dry, and red Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Moons of Mars • Mars has 2 Small Moons • • • Tidally locked Phobos (fear) • • • • prob. captured Asteroids ~22 km diameter NASA/JPL-caltech/University of Arizona 9377 km from mars Stickney crater and parallel grooves Deimos (panic) • • ~12 km diameter 3x further from Mars NASA/JPL-caltech/University of Arizona Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Let’s Practice Mars lost its water because it lost its _____. A. Moons B. Magnetic field C. Oxygen D. Life Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Which of the necessary prerequisites for life (as we understand it) did Mars have in the past? A. Range of necessary chemical elements B. Surface Water C. Both of these D. Neither of these Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 SS Topics: Jovian Planets Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 BRIEF OVERVIEW Giant or Gas Giant or Jovian Planets • • • Formed beyond the frost line, via direct accretion of gas • • Large planets, lots of moons, rings No solid surface! Mostly H & He in liquid or ice form (outer bit gaseous) Belt-zone circulation (stripes) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Key Characteristics of Jupiter • • • • Largest planet Cassini Image of Jupiter (true color mosaic & reprojection) Great Red Spot 4 Galilean Moons Many smaller moons • 50 named, 14 provisional • • Very thin rings • Very strong magnetic field Thin cloudy atmosphere Astronomy 1 - Elementary Astronomy NASA/JPL/University of Arizona LA Mission College Levine F2015 Moons of Jupiter • 50-70 small moons • • likely captured “Family Portrait” 4 Galilean Moons • • • • • Io • Worlds in their own right Europa Ganymede Callisto likely formed along with Jupiter Astronomy 1 - Elementary Astronomy NASA Planetary Photojournal LA Mission College Levine F2015 Rotation of Jupiter • • • Jovian “year” ~ 11.9 Earth years Jovian “day” less than 10 hours • planet is flattened (oblate) Axial tilt ~3° Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Uranus Key Facts • Chance discovery by William Herschel in 1781 • Unusual Rotation • 97° axial tilt -- Extreme Seasons • Composition similar to other gas giants • larger core than Jupiter & Saturn • nonmetallic Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Uranus Key Facts • • Weird magnetosphere • • ~75% Earth’s, • twisted 60° to rotational axis & offset Featureless blue • • • • origin unknown -- water/ amonia/methane dynamo? methane subtle cloud structure Rings similar to Jupiter’s 27 moons discovered, 5 major moons Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Neptune Key Facts • Discovered because Uranus wasn’t behaving! • in 1846 at position predicted from gravitational disturbances on Uranus’s orbit by J. C. Adams and U. J. Leverrier Astronomy 1 - Elementary Astronomy NASA LA Mission College Levine F2015 Neptune Key Facts • • Color similar to Uranus Also has weird magnetosphere • • • tipped, offset, weak, unk. mechanism faint rings NASA 13 moons Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 SATURN Key Characteristics of Saturn • Like Jupiter, mostly H and He • RINGS!!!!!!! • • • Cassini composite image of Saturn Most spectacular and complex Many moons magnetic field • ~20x weaker than Jupiter’s Astronomy 1 - Elementary Astronomy NASA/JPL/Space Science Institute LA Mission College Levine F2015 Rotation of Saturn • • • Rotation period (“Day”) = 10h39m Revolution period (“year”) = 29.5 years Axial tilt 27° Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Current Mission to Saturn • Cassini/Huygens (NASA/ESA) • • 5 Oct 1997: Launch • 24 Dec 2004: Huygens Probe Release • 14 Jan 2005: Huygens Probe Landing 1 Jul 2004: Saturn Orbit Insertion Astronomy 1 - Elementary Astronomy Image Credit: NASA LA Mission College Levine F2015 Moons of Saturn • Largest • • Titan discovered by Christiaan Huygens in 1655 • • Mimas & Enceladus discovered by William Herschel in 1789 Iapetus (1671), Rhea (1672), Dione (1684), and Tethys (1684) discovered by Giovanni Domenico Cassini Hyperion (1848) and Phoebe (1898) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Moons of Saturn • Shepherd Moons • moons on orbits close to the rings focus the ring material, keeping the rings confined or sweeping material out • • • • • Pan (Encke gap) Daphnis (Keeler gap) Atlas (A Ring) Prometheus (F Ring) Pandora (F Ring) Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Saturn’s Rings Cassini Division A C B Encke’s Division • NASA Discovered in 1610, by Galileo • thought they were small moons on either side of the planet • In 1659,Christiaan Huygens proposed that Saturn was circled a ring • In 1675,Jean-Dominique Cassini discovered complex structure • gap between A & B rings Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Saturn’s Rings • • • • 282,000 km wide • separated by empty regions: divisions • ~1 km thick A Ring Dusty water ice particles B Ring 3 main segments: A, B, and C Ring C Ring Cassini Division Rings must be replenished by fragments of passing comets & meteoroids. Rings can’t have been formed together with Saturn • material would have been blown away by particle stream from hot Saturn Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Saturn’s Rings • Rings are composed of ice particles • Much larger than those in Jupiter’s ring • moving at large velocities around Saturn • but small relative velocities (all moving in the same direction). Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 MOONS OF SATURN Titan • Big. 5150 km • bigger than mercury, a bit smaller than Ganymede • Surface T ~ -289 °F(-178°C). • orbits ~ 1.2 million km from Saturn • Titan with Tethys in the background (Cassini Image) NASA/JPL/Space Science Institute 16 day orbital period Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Titan’s Atmosphere • Nitrogen atmosphere!! • • • Thick clouds atmospheric pressure ~60% greater than the Earth's • • Also contains sig. methane and ethane bottom of a swimming pool Cold surface -> methane and ethane can condense • Hydrocarbon rain Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Enceladus Enceladus • Enceladus • • • 500 km diameter tidal flexing & ice vulcanism NASA/JPL/Space Science Institue Cassini current flyby NASA/JPL/Space Science Institue Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Highlighted Smaller Moons Iapetus • Iapetus • • 1500 km diameter black side and white side Credit: NASA/JPL/Space Science Institute Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Highlighted Smaller Moons Mimas • Mimas • • • 400 km diameter Huge Herschel Crater “Death Star” NAS A/ JPL/ Spac e Scien ce Instit Levine F2015 http://images2.fanpop.com/images/photos/ 4500000/Death-Star-starwars-4534240-1280-800.jpg Astronomy 1 - Elementary Astronomy LA Mission College Carolyn Porco talks about Cassini Why you should learn to love the outer solar system Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 TED Talk in 2007 -- Carolyn Porco flies us to Saturn Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Pluto Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015 Pluto • • • • 2/3 diameter & 1/6 the mass of Earth's moon probably has a rocky core surrounded by a mantle of water ice. methane and nitrogen frost coat its surface. Owing to its size and lower density, 248-year-long elliptical orbit a= 49.3 astronomical units (AU) • • • From 1979 to 1999, Pluto was actually closer to the sun than Neptune when Pluto is close to the sun, its surface ices thaw, rise and temporarily form a thin atmosphere. Pluto has a very large moon that is almost half its size named Charon and 4smaller ones Nix, Hydra, Kerberos & Styx Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 WHY PLUTO ISN’T A PLANET A brief History of Non-planets • Ceres was discovered by Father Giuseppe Piazzi in 1801 • • • 1st object in the asteroid belt. Ceres was initially classified as a planet More such objects were found & became known as asteroids Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 A brief History of Non-planets • Pluto Discovered 1930 by C. Tombaugh • ~ 65 % of size of Earth’s Moon Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 A brief History of Non-planets • In 1992 first Kuiper Belt object sighted • More than 1,300 KBOs have been identified since Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 A brief History of Non-planets • Eris discovered in 2003 • • • Palomar Observatory by Mike Brown, Chad Trujillo & David Rabinowitz confirmed in January 2005 submitted to IAU as a possible 10th planet of our solar system • it was the first object in the Kuiper Belt found to be bigger than Pluto. Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 What IS a planet anyway? • The discovery of Eris ultimately led the IAU to come up with a definition of “planet”. • International Astronomical Union Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 What IS a planet anyway? “The IAU members gathered at the 2006 General Assembly agreed that a "planet" is defined as a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.” Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 IAU definitions ctd. “A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.” “All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies" Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Why isn’t Pluto a Planet Anymore? Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Other Dwarf Planets • • • • Ceres Eris Haumea Makemake Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 WRAP-UP Topic for Next Class • • Jovian Planets & Moons Pluto Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Reading Assignment • • Astro:5&6, Astropedia:11&12 Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015 Homework • No new HW yet — very, very soon Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015
