[meteorite-list] Spitzer Telescope Sees Trail of Comet Crumbs (Schwassman-Wachmann 3)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed May 10 19:12:30 2006
Message-ID: <200605102310.QAA26540_at_zagami.jpl.nasa.gov>

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

Image Advisory: 2006-075 May 10, 2006

Spitzer Telescope Sees Trail of Comet Crumbs

NASA's Spitzer Space Telescope has snapped a picture of the
bits and pieces making up Comet 73P/Schwassman-Wachmann 3,
which is continuing to break apart on its periodic journey
around the sun. The new infrared view shows several chunks
of the comet riding along its own dusty trail of crumbs.

"Spitzer has revealed a trail of meteor-sized debris filling
the comet's orbit," said Dr. William T. Reach of NASA's
Spitzer Science Center at the California Institute of
Technology, Pasadena. Reach and his team recently observed the
comet using Spitzer. The picture can be viewed at

http://www.spitzer.caltech.edu/Media/releases/ssc2006-13/ssc2006-13a.shtml .

Comet 73P/Schwassman-Wachmann 3 consists of a collection of
fragments that file along like ducks in a row around the sun
every 5.4 years. This year, the bunch will pass by Earth beginning
on May 12 before swinging by the sun on June 6. The fragments
won't get too close to Earth, about 7.3 million miles, or 30
times the distance between Earth and the moon, but they should
be visible through binoculars in the countryside night skies.

The icy comet began falling apart in 1995 during one of its
tropical trips to the sun. Astronomers believe that its crusty
outer layer cracked due to the heat, allowing fresh ice to
evaporate and split the comet apart.

During the past six weeks, amateur and professional astronomers
have been watching the comet fall apart before their telescopes'
eyes. Spitzer viewed the broken comet from its quiet perch up in
space May 4 to May 6, covering a portion of the sky that allowed
it to spot 45 of the 58 known fragments.

The observatory's infrared view also provides the first look
at the dusty trail left by the disintegrating comet after it
splintered apart in 1995. The trail is made up of comet dust,
pebbles and rocks that occasionally rain down on Earth in what
is called the Tau Herculid meteor shower. From May 19 to June 19,
as Earth passes through the outskirts of the trail, only a weak
meteor shower is expected, with just a few "shooting stars"
visible in the night sky. A larger meteor shower might occur in
2022 if Earth crosses near the comet's wake as predicted.

Spitzer's infrared eyes were able to see the dusty comet bits
lining the trail because the dust is warmed by sunlight and glows
at infrared wavelengths. Most of the dust particles, specifically
the millimeter-sized nuggets, had never been seen before. Reach
said that these particles probably represent the natural
deterioration of the comet over the years, a process commonly
observed in intact comets.

The comet dust also adds up to more evidence for the "icy dirtball"
theory of comets. In recent years, more and more astronomers are
coming to think of comets not as snowballs coated in dust, but as
dirtballs crusted with ice.

"By measuring the brightness and extent of the debris trail, we
are trying to find out whether most of the comet's mass
disintegrates into vapors from evaporating ice, the house-sized
chunks seen in images from the Hubble Space Telescope, or the
meteor-sized debris seen in the Spitzer images," said Reach.

Reach and his team will continue to study the Spitzer data for
clues to how the comet broke up. Their infrared data will tell
them the sizes of the major fragments, which might indicate
whether the comet did, as believed, crack under the thermal
stress.

Comet 73P/Schwassman-Wachmann 3 should be dimly visible through
binoculars on a clear night between the Cygnus and Pegasus
constellations from May 12 to May 28. For more information
about viewing the comet or the meteors, visit

http://science.nasa.gov/headlines/y2006/24mar_73p.htm .

None of the comet's fragments pose a danger to Earth. For more
information, see

http://www.nasa.gov/mission_pages/hubble/Comet_73P.html .

Members of Reach's team include: Dr. Michael Kelley of the
University of Minnesota, Twin Cities; Dr. Carey M. Lisse of
the Johns Hopkins University's Applied Physics Laboratory,
Laurel, Md.; Dr. Mark Sykes of Planetary Science Institute,
Tucson, Ariz.; and Dr. Masateru Ishiguro of the Institute of
Space and Astronautical Science, Japan.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages
the Spitzer Space Telescope mission for NASA's Science
Mission Directorate, Washington. Science operations are
conducted at the Spitzer Science Center at the California
Institute of Technology. Spitzer's multi-band imaging
photometer, which made the observations, was built by Ball
Aerospace Corporation, Boulder, Colo.; the University of
Arizona, Tucson; and Boeing North American, Canoga Park,
Calif. The instrument's principal investigator is Dr. George
Rieke of the University of Arizona.

For more information about NASA and agency programs on the
Web, visit

http://www.nasa.gov/home/ .

-end-
Received on Wed 10 May 2006 07:10:26 PM PDT