MEDIA RELATIONS OFFICE<br />JET PROPULSION LABORATORY<br />CALIFORNIA INSTITUTE OF TECHNOLOGY<br />NATIONAL AERONAUTICS AND SPACE ADMINISTRATION<br />PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011<br />http://www.jpl.nasa.gov<br /> <br />Contact: JPL/Guy Webster (818) 354-6278<br /> University of Hawaii/Karen Rehbock (808) 956-6829<br /><br />FOR IMMEDIATE RELEASE May 17, 2002 <br /><br />ASTRONOMERS DISCOVER 11 MORE SMALL MOONS OF JUPITER<br /><br /> The discovery of 11 small moons orbiting Jupiter <br />leapfrogs the number of that planet's moons to 39, nine more <br />than the record of the previous champ, Saturn.<br /><br /> A team led by astronomers from the University of Hawaii, <br />Honolulu, made the discovery based on images taken in <br />December 2001 and later follow-up observations. Orbits were <br />determined by collaborators at NASA's Jet Propulsion <br />Laboratory, in Pasadena, Calif., and the <br />Harvard-Smithsonian Center for Astrophysics, Cambridge, <br />Mass.<br /><br /> Researchers estimate the new-found natural satellites <br />are each about two to four kilometers (one to two miles) <br />in diameter, and were probably passing rocks captured by <br />Jupiter's gravity long ago.<br /><br /> The discovery-team leaders, Scott Sheppard and <br />Dr. David Jewitt of the University of Hawaii, also <br />discovered 11 other small satellites of Jupiter in 2000.<br /><br /> The new moons were discovered by Sheppard, Jewitt and <br />Jan Kleyna of Cambridge University, England. They used the <br />Canada-France-Hawaii 3.6-meter (142-inch) telescope with <br />one of the largest digital imaging cameras in the world to <br />obtain sensitive images of a wide area around Jupiter.<br /><br /> The digital images were processed and searched using <br />computers. Candidate satellites were monitored in the <br />succeeding months at the University of Hawaii's 2.2-meter <br />(88-inch) telescope to confirm their orbits and to reject <br />asteroids masquerading as satellites.<br /><br /> JPL's Dr. Robert Jacobson and Harvard-Smithsonian's <br />Dr. Brian Marsden determined the satellites' irregular -- <br />highly elongated and tilted -- orbits. All 11 objects <br />orbit in the direction opposite to the rotation of the <br />planet.<br /><br /> The orbits of the irregular satellites strongly <br />suggest an origin by capture. Since no efficient <br />contemporary capture mechanisms are known, it is likely <br />that the irregular satellites were acquired when Jupiter <br />was young, possibly still in the process of condensing <br />down to its equilibrium size. As yet, nothing is known <br />about their surface properties, compositions or densities, <br />but they are presumed to be rocky objects like the <br />asteroids.<br /><br /> The new discoveries bring the known total of <br />Jovian satellites to 39, of which 31 are irregulars. The <br />eight regular satellites include four large moons discovered <br />by the astronomer Galileo Galilei and four smaller moons on <br />circular orbits closer to Jupiter. Jupiter's nearest rival <br />for having the largest number of known satellites is Saturn, <br />with 30, of which 13 are irregular.<br /><br /> The satellites were formally announced by the <br />International Astronomical Union on Circular No. 7900 <br />(May 16, 2002). More information about them is available <br />online from the University of Hawaii at <br /><br />http://www.ifa.hawaii.edu/~sheppard/satellites/jup.html . <br /><br />Other information about the Jupiter system is available <br />from JPL at <br /><br />http://www.jpl.nasa.gov/solar_system/planets/jupiter_index.html .<br /><br /> The Institute for Astronomy at the University of Hawaii <br />conducts research into galaxies, cosmology, stars, planets <br />and the Sun. The Canada-France-Hawaii telescope is funded by <br />the University of Hawaii and the governments of Canada and <br />France. JPL, a division of the California Institute of <br />Technology, Pasadena, is NASA's lead center for robotic <br />exploration of the solar system.<br /><br /># # # # #