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SOLAR SYSTEMS CHAPTER 21 definition • Objects that revolve around a star • Major members – Planets – Moons • Minor members – Dwarf planets – Asteroids – Comets – meteoroids What is a planet? (as of Aug. 2006) • The IAU said that the definition for a planet is now officially known as "a celestial body that • (a) is in orbit around a star • (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a (nearly round) shape and • (c) has cleared the neighborhood around its orbit." (not in a swarm of rocks) Our solar system scoreboard • • • • • Planets= 8 Moons= 167 Dwarf planets= 5 Asteroids= 536,000+ Comets= 3,062 Exosolarsystems • Other solar systems • 661 new solar systems confirmed! • Over 3000 planets (exoplanets) First discovered in 1995 Estimated over 50 BILLION Earth like planets (habitable zone) • Maybe 2? • Gliese D – 6x more massive than earth “superearth” – In Libra – 20 lya • HD 85512 b – In Vela – 26 lya HOW DO ASTRONOMERS FIND NEW PLANETS??????? Radial Velocity • Planets are detected by studying light shifts due to star wobbles • Uses Doppler Effect – Red light moves AWAY – Blue light moves TOWARDS Astrometry • Measures star wobbles from geometry Transit method • Planet blocks star (eclipse) • Light from star is lessen • Kepler mission Optical detection • Block star’s light out using a chronograph List of exoplanets • http://exoplanet.eu/catalog/ Exoplanet missions • Kepler- launched 2009 • Has found 77 planets so far METHODS to find a new planet • http://planetquest.jpl.nasa.gov/Planet_Finder /planetfinder.html Other research • LBT (large binocular telescope) • Keck telescopes (Hawaii) • Spitzer Space Telescope – Infrared telescope OUR SOLAR SYSTEM Our solar system The planets drawn to scale INNER PLANETS INNER PLANETS • • • • Terrestrial Rocky No rings Smaller compared to Outer planets MERCURY • No atmosphere • Temperatures fluctuate wildly • MESSANGER is currently orbiting Mercury- has completed 282 orbits (so far!) Sept. 29, 2009 MESSANGER Messenger 9/21/11 • Mapping surface of Mercury MESSANGER IMAGE Aug. 23. 2012 VENUS • THICK atmosphere – Hot! – Crushing pressure • Rotation is retrograde – Sun rise in west; set in east Pancake volcanoes MARS • Thin atm. • Windy • Surface similar to Earth – Volcanoes – Old river valleys- where’s the water? – Best chance to find fossil (life?) in SS Opportunity and Spirit • http://marsrovers.jpl.nasa.gov/home/ CURIOSITY landed Aug. 6, 2012 CURIOSITY CONFIRMS WATER ONCE FLOWED!! Mars Moons • Phobos • Deimos Jovian Planets • • • • • Outer planets Large Many moons all have rings Made of gas JUPITER • Often captures comets/asteroids – Shoemaker/Levy comet (1994) Jupiter’s Ring system Feb. 2007 Jupiter’s New Moons • Jupiter now has 63 known moons • 23 moons were discovered in 2002-3 by Earth-based telescopes http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Moons Saturn’s Rings • Made of Water ice and dust • Sheppard moons keep rings in place Uranian Weirdness A few of Uranus’s moons MIRANDA ARIEL PUCK OBERON Neptune • Very active weather Triton- • • • • Liquid nitrogen volcanoes Cantaloupe terrain Underground oceans? Alien life? Planet ? • 2003 UB313 • Renamed Eris (Xena) What is a planet? (as of Aug. 2006) • The IAU said that the definition for a planet is now officially known as "a celestial body that • (a) is in orbit around a star • (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a (nearly round) shape and • (c) has cleared the neighborhood around its orbit." (not in a swarm of rocks) Pluto • Dwarf planet Lowell Observatory where Pluto was discovered 1939 Plutoids • Dwarf planets beyond Neptune • Established in 2008 Planets, dwarf planets, plutoids How many moons does Pluto have? We’re on the way… • New Horizons spacecraft was launched in Jan. 2006 • Will arrive at Pluto July 2015