Exploring The Planets - What's New In Planetary Exploration

September, 2006

PLUTO DOWNGRADED


	Pluto Loses Planetary Status Recent discoveries of large objects orbiting the Sun beyond Neptune and Pluto have prompted the International Astronomical Union (IAU) to re-examine the way planetary bodies are classified. On August 24, 2006, the IAU passed a resolution redefining the criteria for planetary status. A planet is defined by three properties. 1) It is a celestial body that orbits the Sun. 2) It is massive enough that its own gravity causes it to form in a spherical shape. 3) It has cleared the neighborhood around its orbit. Under this definition, our Solar System has eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Because Pluto resides in an area of space populated by numerous other objects, it is no longer considered a planet. Pluto is now designated a dwarf planet, and it is the prototype of a class of objects located beyond the orbit of Neptune. Image courtesy of Center for Earth and Planetary Studies/National Air and Space Museum/Smithsonian Institution

Former What's New Topics: The Latest in Planetary Missions August, 2006 Planetary Mission Udpates March, 2006 MESSENGER Udpate June, 2005 Deep Space Missions January, 2005 Stardust January, 2004 Stardust September, 2002 A Closer Look at a Volcano on Io November, 1999 NASA Approves Mission To Mercury July, 1999 First Image From Landsat 7 Earth Remote Sensing Satellite April, 1999 Mars Global Surveyor Mapping Mission Begins March, 1999 STARDUST: Mission To A Comet February, 1999. Galileo Reveals Process Behind Formation of Jupiter's Rings September 15, 1998. Possible Extrasolar Planet Imaged by the NASA Hubble Space Telescope May 28, 1998