[meteorite-list] Palomar Observatory's 200-inch Hale Telescope Observes Comet Impact

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Jul 21 19:01:52 2005
Message-ID: <200507212301.j6LN13Y11043_at_zagami.jpl.nasa.gov>

Caltech News Release
For Immediate Release
July 21, 2005

Deep Impact: During and After Impact

PALOMAR MOUNTAIN, Calif. - Astronomers using the Palomar
Observatory's 200-inch Hale Telescope have been amazed by comet
Tempel 1's behavior during and after its collision with the Deep
Impact space probe.

In the minutes just after the impact the comet was seen to increase
its near-infrared brightness nearly fivefold. As the event
progressed astronomers at Palomar were able to distinguish jets of
material venting from the comet's nucleus that have persisted for
days.

Early results from the data, in images taken just minutes after
impact, showed a possible plume of dust and gas extending outward
some 320 km (200 miles) from the comet's center, roughly coinciding
with the site of the probe's final demise.

This apparent dust plume has persisted for several nights, allowing
astronomers to watch the comet's slow rotation. The night after
impact the plume was on the far side of the comet, but was visible
again the next evening as the comet's rotation brought it back into
view. Two days after impact, the plume was seen again, this time
extending about 200 km (124 miles) from the comet's center.
According to Bidushi Bhattacharya of the California Institute of
Technology's (Caltech) Spitzer Science Center, "This could be
indicative of an outburst of gas and dust still taking place near the
region of the impact."

"We are very excited by these results. It is a fabulous time to be
studying comets," says James Bauer of the Jet Propulsion Laboratory
(JPL). "It will be interesting to see how long the effects of the
impact persist," he adds.

The images of the comet, obtained by Bauer and Bhattacharya, were
sharper than those from most ground-based telescopes because they
used a technique known as adaptive optics. Adaptive optics allows
astronomers to correct for the blurring of images caused by Earth's
turbulent atmosphere, giving them a view that often surpasses those
of smaller telescopes based in space.

Using the adaptive-optics technique to improve an astronomer's view
is generally only possible when a bright star is located near the
object they want to study. On the night of impact there was no bright
star close enough to the comet to use. Mitchell Troy, the
adaptive-optics group lead and Palomar adaptive-optics task manager
at JPL, worked with his team to make adaptive optics corrections
anyway. "Through the dedicated efforts of the JPL and Caltech teams
we were able to deploy a new sensor that was 25 times more sensitive
then our normal sensor. This new sensor allowed us to correct for
some of the atmosphere's distortions and significantly improve the
view of the comet," says Troy. This improved view allowed astronomers
to see the dust and ejected material moving out from the comet's
surface immediately following the impact event and again days later.

Earth-based observations from telescopes like the 200-inch at Palomar
give astronomers an important perspective on how the comet is
reacting to the impact, a perspective that cannot be achieved from
the front-row seat of a fly-by spacecraft. Astronomers on the ground
have the luxury of long-term observations that may continue to show
changes in the comet for weeks to come.

Collaborators on the observations include Paul Weissman (JPL), and
the Palomar 200-inch crew. The Caltech-adaptive optics team is made
up of Richard Dekany (team leader), Antonin Bouchez, Matthew Britton,
Khanh Bui, Alan Morrissett, Hal Petrie, Viswa Velur and Bob Weber.
The JPL Palomar adaptive-optics team includes Mitchell Troy (team
leader), John Angione, Sidd Bikkannavar, Gary Brack, Steve Guiwits,
Dean Palmer, Ben Platt , Jennifer Roberts, Chris Shelton, Fang Shi,
Thang Trinh, Tuan Truong and Kent Wallace.

The Palomar adaptive-optics instrument was built and continues to be
supported by the Jet Propulsion Laboratory as part of a Caltech-JPL
collaboration.

Support for the adaptive-optics research at Caltech's Palomar
Observatory comes from the Oschin Family Foundation, the Gordon and
Betty Moore Foundation and the National Science Foundation Center for
Adaptive Optics.

Images are available at:
http://www.astro.caltech.edu/palomarnew/deepimpact.html


MEDIA CONTACT: Scott Kardel, Palomar Public Affairs Director
                (760) 742-2111
                wsk_at_astro.caltech.edu
Received on Thu 21 Jul 2005 07:01:02 PM PDT


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