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AST-L13-ch8__3

AST-L13-ch8__3 - Chicxulub AST 1002 Planets Stars and...

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1 Pluto & Space Debris Today’s Lecture: purpose & goals AST 1002 Planets, Stars and Galaxies describe what we have learned about Pluto orbit size , & composition atmosphere presence of moon gain an understanding of Space Debris . Kuiper-Belt Objects Comets Meteoroids Asteroids Planetarium show “Doomsday Asteroid” The Barringer Meteor Crater (Arizona) Chicxulub Review Cassini-Huygens S aturn and i t s moon s Big, Bigger, Biggest!! –– Uranus, Neptune, Saturn, and Jupiter Massive and cold composition – mostly hydrogen & helium Great internal pressure Enough to compress hydrogen into a form called liquid metallic hydrogen liquid metallic hydrogen. Powerful magnetic fields Incredibly strong winds & powerful cyclonic activity e.g. Great Red Spot Powerful gravitational forces -- origin of ring systems Roche Limit ~2 ½ planetary radii All jovian planets have ring systems and many moons must know distinguishing properties of Io, Europa, Titan, and Triton What we know about Pluto: HOW we l earned about P l uto : Photographs of planet’s motion among stars Occultations Where the motion of the planet in orbit brings it across the position of a star, blocking it as seen from earth . Eclipses (and observations of the motion of the planet and its moon) Where the motion of the planet and its moon bring each of them across the position of the other, blocking it as seen from earth . What do the s e ob s ervat i on s te ll u s ? WHAT i t ha s taught u s : Planet’ orbital path and period Presence of the moon Charon Planet’s mass Planet’s diameter (size) Planet’ density Presence of an atmosphere Presence of surface features
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2 Pluto Discovered by Clyde Tombaugh (U.S. Naval Observatory) in 1930 based on mathematical prediction of gravitational effect on Neptune and Uranus. compared images of star-fields to see motion Farthest planet from the Sun (most of the time) occasionally is closer than Neptune (highly elliptical , tilted orbit ) orbit takes 248 Earth years Moon (Charon ) discovered by telescopic image closer together that the resolution limit of almost all telescopes best images made by the Hubble space Telescope HST image
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