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Astronomers Discover Moon Orbiting Asteroid
(Images in various formats are available here.)
The above infrared image is a composite of 5 detections of the new moon (taken -- clockwise from top -- on the nights of 1998 Nov 6,7,9,10 and 1). The green dashed line shows the orbit of the moon around the primary asteroid (45)Eugenia. The period of the orbit is 4.7 days. The moon travels in a closewise direction in this view. The radius of the nearly circular orbit is about 1200 km. The orbit is tilted about 45 degrees with respect to our line-of-sight, so it appears as an oval. The main asteroid is about 215 km in diameter and we estimate the moon's diameter to be 13 km. The moon is 300 times fainter than the asteroid. The large "cross" is a common artifact caused by stray light in the telescope, and is not a real object. Utilizing a new technology, called adaptive optics, we have been able to achieve images 6 times sharper than could otherwise have been obtained from the Earth's surface. Adaptive optics detects and removes the blurring caused by the Earth's atmosphere. Images are obtained at the Canada-France-Hawaii Telescope located on Mauna Kea, Hawaii. Photo credit: Laird Close (European Southern Observatory, Munich, Germany), Bill Merline (Southwest Research Institute, Boulder, CO USA)
The above infrared image (1.6 microns) is a superposition of 5 detections of the new moon (taken --clockwise from top-- on the nights of Nov 1998, 6, 7, 9, 10, and 1 UT). The blue dashed line shows the orbit of the moon around the primary asteroid (45) Eugenia. The period of the orbit is 4.7 days. The moon travels in a clockwise direction (with North up and East to the left). The radius of the orbit is 1190 km. The main asteroid's diameter is close to 215 km (depicted here as a central white circle) and we estimate the moon's size is 13 km in diameter. The moon is 285 times fainter than the main asteroid and is very close to the main asteroid (just over 5 asteroid diameters away, or 0.77 arcseconds on the sky). Image processing (deconvolution) was used to increase the contrast between the moon and the main asteroid. The apparent variations in the moon's brightness and size are artificially produced due to changes in the atmospheric clarity from night to night.
Utilizing adaptive optics this image (resolution of approximately 185 km or 0.12 arcseconds on the sky) is 6 times sharper than could have been otherwise obtained from the ground. Images taken with the PUEO adaptive optics system of the Canada-France-Hawaii Telescope located on Mauna Kea, Hawaii.
Photo Credit: Laird Close (European Southern Observatory, Munich, Germany), Bill Merline (Southwest Research Institute, Boulder, CO, USA)
Dr. William J. Merline merline@boulder.swri.edu
Southwest Research Institute
Boulder CO USA
Dr. Laird Close lclose@eso.org
European Southern Observatory
Munich, Germany
Dr. Christophe Dumas dumas@hokulewa.jpl.nasa.gov
Jet Propulsion Laboratory
Pasadena, CA USA
Dr. Clark R. Chapman cchapman@boulder.swri.edu
Southwest Research Institute
Boulder, CO USA
Dr. Francois Roddier roddier@ifa.hawaii.edu
Institute for Astronomy
University of Hawaii
Honolulu, HI USA
Dr. Francois Menard menard@cfht.hawaii.edu
Canada-France-Hawaii Telescope Corp.
Kamuela, HI USA
Dr. David Slater dslater@swri.edu
Southwest Research Institute
San Antonio, TX USA
Dr. Gilles Duvert duvert@obs.ujf-grenoble.fr
Laboratoire d'Astrophysique de Grenoble
Grenoble, France
Dr. Chris Shelton cshelton@keck.hawaii.edu
W.M. Keck Observatory
Kamuela, HI USA
Dr. Tom Morgan tmorgan@hq.nasa.gov
NASA Headquarters
Washington, DC USA
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Last updated 06-Oct-1999 by Will Colwell