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Hubble Finds New Asteroid Moon

This is the discovery image, taken March 1 at 0548 UT, using the WFPC2 instrument on HST with the F439W ("B") filter-- central wavelength 439 nm. This is a subsection of the PC1 chip, 0.046 arcsec per pixel. North is almost straight up (13 deg. CCW) and East to the left. The image has been strongly stretched to show the companion, so that the primary asteroid and surrounding pixels are all white.
by Mark Perew
Los Angeles - March 21, 2001
Asteroid (107) Camilla has joined the ranks of asteroids boasting a small moon. Astronomers from Towson University in Maryland found the satellite in five images taken by the Hubble Space Telescope earlier this month.

While it is too early to have precise mass and orbit data, the images do show that the new moon, provisionally dubbed S/2001 (107) 1, is probably of the same type as its primary. The images also imply a size ratio of 1:25.

"These images were taken by a snapshot program filling up available time on HST," reported Professor Alex Storrs. "This is part of a campaign to study main belt objects for companions and surface variegations. These observations are complementary with, not in competition to, ground based observations."

While the ground based observations using the Keck adaptive optics system, for example, are excellent in the infrared, Hubble uses visible light. Both systems, Prof. Storrs stressed, reveal useful data about the objects being studied.

Of the asteroids found to have large satellites, all appear to be "primitive" types. To Prof. Storr, this implies that they are unadulterated both physically and dynamically.

"They can't have had large impacts or close passes," he explained. "They are, I'd venture to say, pristine."

"This is an interesting time to be studying asteroids." Professor Storr stated. For so many years we've struggled with the limits of resolution [of ground based telescopes]. Now with adaptive optics, HST and Doppler radar the field has become interesting all over again."

Additional HST images will be taken next week. To date only 10% of the roughly 50 objects have been imaged in this observing campaign.

Mark Perew is a freelance science writer, a member of the National Association of Science Writers and a JPL Solar System Ambassador. He is also creating the ScienceMakers website.

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Adaptive Optics Reveals Astroidal Satellite
Pasadena - March 7, 2001
Yet another of the rare astroidal binaries has been spotted. Caltech astronomers Mike Brown and Jean-Luc Margot found the newly discovered moon orbiting asteroid (87) Sylvia which joins only six other known asteroids with companions.