From: LARRY KLAES (ljk4_at_msn.com)
Date: Thu Sep 15 2005 - 15:34:02 UTC
>From: cunews_at_cornell.edu
>Reply-To: cunews_at_cornell.edu
>To: CUNEWS-PHYSICAL_SCIENCE-L_at_cornell.edu (CUNEWS-PHYSICAL_SCIENCE-L),
> CUNEWS-SCIENCE-L_at_cornell.edu (CUNEWS-SCIENCE-L)
>Subject: Featuring Cornell: Ceres upgraded to miniplanet
>Date: Thu, 15 Sep 2005 10:58:13 -0400
>
>Asteroid or miniplanet? Cornell astronomer finds Ceres appears to have
>shape and interior similar to terrestrial planets
>http://www.news.cornell.edu/stories/Sept05/Ceres.to.html
>
>Sept. 15, 2005
>
>By Thomas Oberst
>cunews_at_cornell.edu
>
>
>ITHACA, N.Y. -- When is a space rock more than just a space rock?
>
>Ceres 1 was already holding the title of the solar system's largest
>asteroid. Now new observations show the space rock may be more worthy of
>the appellation "miniplanet."
>
>On Sept. 7 NASA released photographs of Ceres that show the rock is a
>smooth ellipsoid, or oblong sphere, with an average diameter of
>approximately 590 miles -- about the size of Texas. A scientific paper on
>the findings, by a group led by Peter C. Thomas, senior research associate
>at Cornell University's Center for Radiophysics and Space Research,
>appeared in the Sept. 9 issue of the journal Nature.
>
>Co-author Joel Parker, an astronomer at the Southwest Research Institute in
>Boulder, Colo., used the Hubble Space Telescope's Advanced Camera for
>Surveys to snap 267 images of Ceres on Dec. 28, 2003, during a nine-hour
>period -- one Ceres "day."
>
>Being ellipsoid and smooth is special for a rock. It indicates that the
>body is heavy enough to possess gravity strong enough to suck its own
>surface smooth -- a process called "gravitational relaxing." Because the
>process typically requires a mass of many trillions of tons, depending on
>the temperature, the average pebble is not going to be gravitationally
>relaxed; even most asteroids aren't.
>
>By combining the new information on Ceres' roundness with previous
>independent measurements of its mass, Thomas and his colleagues inferred
>that Ceres must have a "differentiated interior" similar to the terrestrial
>planets. Although this possibility had been previously predicted, it was
>not widely accepted. "We used the best telescope available to apply a basic
>geophysical test of other people's predictions," Thomas said.
>
>Based on their own models and observations, Thomas and his colleagues
>believe Ceres contains a rocky silicate core and icy mantel covered by a
>crust of carbon-rich compounds and clays. Furthermore, they predict that
>the icy mantel may contain more frozen water than all of the fresh water on
>Earth.
>
>Whenever water is mentioned, people ask about life. But Thomas says the
>possibility is "very remote," noting that even if the interior of Ceres
>were warm enough for some of the water to liquefy, Ceres probably lacked a
>sufficient energy source for life to develop.
>
>Ceres was discovered in 1801 by Sicilian astronomer Giuseppe Piazzi and
>declared to be the "missing planet" predicted between Mars and Jupiter.
>However, the title was revoked in 1802 when Ceres was found to be a member
>of the hundreds of thousands of other rocks and debris of the Asteroid
>Belt.
>
>Since the discovery of 2003 UB313 -- which some have hailed as the tenth
>planet -- in July, some astronomers (and many non-astronomers) have begun
>to question whether objects such as Ceres should also be enshrined as
>planets.
>
>Thomas professes a lack of concern about Ceres' place in the solar system.
>"There are plenty of other interesting things and processes in Ceres to
>contemplate rather than whether or not it should be called a planet," he
>said. But for those who prefer a more definitive answer, Thomas offers:
>"You can call Ceres a 'minor planet' or 'miniplanet' if you'd like, but I
>would not call it a 'full-fledged planet.'"
>
>The other authors of the Nature paper are L.A. McFadden of the University
>of Maryland, S.A. Stern and E.F. Young of the Southwest Research Institute,
>C.T. Russell of the University of California-Los Angeles and M.V. Sykes of
>the Planetary Science Institute, Tuscon, Ariz. Funding for the project was
>provided by NASA through the Space Telescope Science Institute.
>
>Thomas Oberst is a writing intern at the Cornell News Service.
>
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