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

[Ron Baalke]

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