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Small Worlds Ceres and Vesta
| Title |
Small Worlds Ceres and Vesta |
| Explanation |
Ceres [ http://www.planetary.org/explore/topics/asteroids_and_comets/ ceres.html ] and Vesta [ http://hubblesite.org/newscenter/archive/releases/ 1997/27 ] are, respectively, only around 950 kilometers and 530 kilometers in diameter - about the size of Texas and Arizona. But they are two of the largest of over 100,000 minor bodies [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ asteroidfact.html ] orbiting in the main asteroid belt [ http://www.solstation.com/stars/ asteroid.htm ] between Mars and Jupiter. These remarkably detailed Hubble Space Telescope images [ http://hubblesite.org/newscenter/archive/releases/ 2007/27/ ] show brightness and color variations across the surface of the two small worlds. The variations could represent large scale surface features or areas of different compositon. The Hubble image data will help astronomers plan for a visit by the asteroid-hopping Dawn spacecraft [ http://dawn.jpl.nasa.gov/index.asp ], scheduled for launch on July 7 and intended to orbit first Vesta [ http://antwrp.gsfc.nasa.gov/apod/ap070525.html ] and then Ceres [ http://antwrp.gsfc.nasa.gov/apod/ap060821.html ] after a four year interplanetary cruise. Though Shakespeare [ http://www.phrases.org.uk/meanings/305250.html ] might not have been impressed, nomenclature introduced by the International Astronomical Union in 2006 classifies nearly spherical Ceres as a dwarf planet [ http://en.wikipedia.org/wiki/Dwarf_planet ]. |
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Dawn Launch Mosaic
| Title |
Dawn Launch Mosaic |
| Explanation |
Shortly after sunrise [ http://www.nasa.gov/mission_pages/dawn/news/ dawn-20070927a.html ] on Thursday at Cape Canaveral [ http://www.nps.gov/nr/travel/aviation/cap.htm ] Air Force Station, the Dawn spacecraft [ http://www.nasa.gov/mission_pages/dawn/spacecraft/index.html ] began its journey to the asteroid belt, arcing eastward into a blue and cloudy sky. Dawn's voyage began on a conventional, chemically fueled [ http://exploration.grc.nasa.gov/education/rocket/ combst1.html ] Delta II rocket [ http://exploration.grc.nasa.gov/education/rocket/ bgmr.html ], but will continue with an innovative ion propulsion system [ http://dawn.jpl.nasa.gov/mission/ion_engine_interactive/ index.html ]. The spacecraft's extremely efficient ion engines [ http://science.nasa.gov/headlines/y2000/ast15jun_1.htm ] will use electricity derived from solar power to ionize xenon atoms and generate a gentle but continuous thrust. After a four year interplanetary cruise, Dawn will orbit two small worlds [ http://antwrp.gsfc.nasa.gov/apod/ap070622.html ], first Vesta and then Ceres. Vesta is one of the largest main belt asteroids, while nomenclature introduced by the International Astronomical Union in 2006 classifies nearly spherical Ceres as a dwarf planet [ http://solarsystem.nasa.gov/planets/ profile.cfm?Object=Dwarf&Display=OverviewLong ]. |
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