[meteorite-list] The Fuzzy Face Of Ceres

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:48:11 2004
Message-ID: <200110122212.PAA11312_at_zagami.jpl.nasa.gov>

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         SKY & TELESCOPE'S NEWS BULLETIN - OCTOBER 12, 2001
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THE FUZZY FACE OF CERES

When Guiseppe Piazzi discovered Ceres on January 1, 1801, he believed
he'd found the planet hypothesized to orbit between Mars and Jupiter.
Although Ceres is no planet, it turned out to be the largest body in
the asteroid belt. And now, two centuries later, astronomers finally
have a crude idea of what its surface looks like.

Thanks to the optical prowess of the Hubble Space Telescope, a team of
observers led by Joel W. Parker (Southwest Research Institute)
captured several images of Ceres on June 25, 1995, in ultraviolet
light (at which HST affords the best resolution). Previous
ground-based observations had resolved Ceres' disk, but only crudely,
using adaptive optics; by contrast, Hubble's images reveal details as
small as 50 kilometers across. Apparently the side of Ceres recorded
by HST is rather bland, except for one dusky dark marking about 250 km
across. As Parker and his colleagues describe in the forthcoming
January 2002 issue of the Astronomical Journal, it's unclear whether
this spot is a crater, a dark area, or something else. But they
believe it's a real feature, enough so to propose that it be named
Piazzi.

The 5-hour HST run was not long enough to follow Ceres through an
entire 9.1-hour rotation, but the pictorial coverage suggests a mean
diameter of 950 ± 8 km. From that, as well as previous mass estimates,
the team determined that Ceres' mean density is roughly 2.6 g/cm^3 --
a reasonable match to the rocky, carbon-enriched composition suggested
by the asteroid's spectrum. Ceres occupies a roughly circular orbit
that averages 2.8 astronomical units (414 million km) from the Sun.


[snip]

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Received on Fri 12 Oct 2001 06:12:02 PM PDT