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Astronomical birth event results in a multitude of 'baby' comets


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POSTED: Thursday, September 17, 2009

Astronomers who were dazzled by the 2007 explosion of a comet into the largest object in the solar system have discovered it gave birth to a bunch of baby comets.

Reporting the “;largest comet birth ever seen”; were David Jewitt, Rachel Stevenson and Jan Kleyna, who observed the event through a Mauna Kea telescope.

Jewitt, a professor, and Stevenson, his graduate student, left the University of Hawaii Institute for Astronomy this summer to join the University of California, Los Angeles. Kleyna is an astrobiology postdoctoral researcher at the institute.

They and others on an institute team observed the spectacular outburst of Comet 17P/Holmes in October and November 2007 from the Canada-France-Hawaii Telescope on Mauna Kea.

The normally obscure comet burst from a tiny nucleus of ice and rock into an object larger than the sun. The astronomers measured the mass of ejected dust at 900,000 miles across. The diameter of the sun, by comparison, is 865,000 miles.

“;It was quite an event,”; Kleyna said in an interview yesterday. “;We got some very high-quality data with a very large camera on the CFH Telescope.”;

He said the astronomers digitally enhanced the images and “;over several nights found these bright spots”; flying away from the nucleus of the comet at speeds of up to 280 mph.

“;We concluded these probably were pieces of icy substance expelled from Comet Holmes like mini-comets,”; he said.

If they were solid chunks of ice they would have been invisible but they were bright with activity, creating their own dust clouds as surface ice vaporized and transformed into gas, Kleyna said.

“;There have been some fragmented comets,”; Kleyna said, “;but I don't think we've seen an eruption that generated many comets before.”;

“;Initially, we thought this comet was unique simply because of the scale of the outburst,”; Stevenson said in a statement. “;But we soon realized that the aftermath of the outburst showed unusual features, such as these fast-moving fragments that have not been detected around other comets.”;

The team continued observing for several weeks. Jewitt, in a Star-Bulletin interview in 2007, said the comet was expanding at about 1,100 mph and was “;an unprecedented million times brighter”; than before.

What the astronomers saw was “;just awesome,”; Jewitt said, and “;very, very weird. An outburst by a factor of a million is staggering, and I don't know of a previous case like this,”; he said as he and his team studied the expanding comet.

Sightings of the baby comets were reported at the European Planetary Science Congress this week in Potsdam, Germany.

Comet Holmes was discovered in an outburst in November 1892, then again in January 1893, probably when the comet was at its closest to the sun, Jewitt said in 2007.

It takes Comet Holmes about six years to circle the sun, traveling between the inner edge of the asteroid belt to beyond Jupiter. Its next closest approach to the sun will be in 2014.

Kleyna said the astronomers are still analyzing data from the 2007 observations. “;There are other interesting details of the comet we're looking at.”;