Tempel to the Telescopes
Summary (Jul 04, 2005): Two space-based assets, the Hubble Telescope and the European X-ray observatory, closely monitored the first ballistic impact of a comet. The early results show a icy interior and perhaps the large debris cloud points towards a harder model for the comet nucleus itself rather a slush or loose rubble pile.

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Tempel to the Telescopes

based on ESA reports

X-ray view of comet Tempel 1 in movie frames. Credit: NASA/JPL

Images taken by the Optical Monitor on board ESA's XMM-Newton observatory on 3 and 4 July 2005, show a comparison between the states of the comet before and just after impact.

The images were taken in the blue and ultraviolet channels of the instrument. The ultraviolet images show the emissions of hydroxyl ions, the direct decay product of water.

About 1.5 hours after the impact, the brightness of hydroxyl groups is increased by a factor of about five. Later, about 4.5 hours after the impact the ultraviolet emission is decreased again which indicates that the peak has passed.

The presence of water in Tempel 1 is consistent with preliminary measurements of the composition of the comet made last week by the ALICE instrument on ESA's Rosetta spacecraft.

The NASA/ESA Hubble Space Telescope also captured the dramatic effects of the collision early July 4 between a 370-kilogram projectile released by the Deep Impact spacecraft and comet 9P/Tempel 1.

The sequence of images shows the comet before and after the impact. The image shows the comet 10 minutes before the impact. The encounter occurred at 7:52 a.m. CEST

In an image captured 15 minutes after the collision, Tempel 1 appears four times brighter than in the pre-impact photo. Astronomers noticed that the inner cloud of dust and gas surrounding the comet's nucleus increased by about 200 kilometers in size.

Tempel 1 coma seen by Hubble after significant brightening caused by debris. Credit: U.Md/NASA/JPL

The impact caused a brilliant flash of light and a constant increase in the brightness of the inner cloud of dust and gas.

The Hubble telescope continued to monitor the comet, snapping another image 62 minutes after the encounter. The gas and dust ejected during the impact expanded outward in the shape of a fan. The fan-shaped debris is travelling at about 1,800 kilometers an hour, or twice as fast as the speed of a commercial jet. The debris extends about 1,800 kilometers from the nucleus.

The potato-shaped comet is 14 kilometers wide and 4 kilometers long. Tempel 1's nucleus is too small even for the Hubble telescope to resolve.

The visible-light images were taken by the Advanced Camera for Surveys' High Resolution Camera.

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Related Web Pages

Deep Impact
ESA Rosetta
Cometary Big Dig
Griffith Observatory Observing Guide to Comet Tempel 1
Blasting Cap On A Comet
Bombing the Comet

Note: Meteors, Asteroids and Comets

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Monday, July 04, 2005