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Venus The bright and morning (evening) star. Moon & Venus Morning of April 22, 2009 http://www.bar-jobservatory.com/Moonvenus.html General Properties • • • • • • 2nd planet form Sun Distance from Sun 0.72 AU Radius: 6,051km or 0.95 Earths Mass: 0.82 Earths Density: 5.24 g/cm3 Average Temperature: 740 Kelvin (~470 C or 880 F) • Number of Moons: 0 • Rotation: -243 days • Orbital Period: 226.5 days or 0.62 years. Phases of Venus • Inferior planet • Angular size changes • Brightness changes Phases of Venus • Evidence that Copernicus was correct. • First observed by Galileo. Alignments of Venus http://planet-venus.info/index.php?document_id=100 Greatest Elongations • Elongations occur when an inner planet's, like Venus, position in its orbital path is at tangent to the view from Earth. • Greatest eastern elongation occurs in western sky • Greatest western elongation occurs in morning sky. http://planet-venus.info/index.php?document_id=710 Elongation of Venus & Mercury March 29, 2004 Credit & Copyright: Jimmy Westlake (Colorado Mountain College) Atmosphere of Venus • Venus has a thick cloudy atmosphere the prevents direct viewing of its surface. Atmosphere of Venus • Venus has a very thick carbon dioxide atmosphere with a surface pressure 90 times Earth’s • Layer of Sulfuric acid. • Slow rotation produces very weak Coriolis effect and little weather Greenhouse Effect • Visible light passes through atmosphere and warms planet’s surface. • Surface heats up from incoming light. • Surface reemits in shorter infrared waves. • Atmosphere and absorbs this infrared light from surface, trapping heat. Atmosphere of Venus Runaway Greenhouse Effect • Venus closer to Sun than Earth. • Atmosphere is mostly carbon dioxide, a greenhouse gas. Runaway Greenhouse Effect • Runaway greenhouse effect would account for why Venus has so little water What have we learned? • What is Venus like today? – Venus has an extremely thick CO2 atmosphere – Slow rotation means little weather • How did Venus get so hot? – Runaway greenhouse effect made Venus too hot for liquid oceans – All carbon dioxide remains in atmosphere, leading to a huge greenhouse effect Landscapes of Venus Radar Mapping Landscapes of Venus Venera Landers Landscapes of Venus Magellan Mission Volcanoes Landscapes of Venus Magellan Mission Volcanoes Landscapes of Venus Magellan Mission Impact Craters
