Telescopes Catch Comet Break Up

May 11, 2006— Giant telescopes around the world are capturing more spectacular views of the near-Earth disintegration of Comet 73P/Schwassman-Wachmann 3. The comet, now comprised of scores of fragments and zillions of tinier pieces, makes its 7.3-million-mile closest approach to Earth on Friday.

A new Spitzer Space Telescope infrared image of the unfolding destruction captures what looks like a line of steam engines following a common cosmic track.

Each "engine" is a comet fragment boiling away plumes of dust and gas as they are blasted by the solar wind. The track the fragments are following is a line of sun-warmed comet debris — dust and fine sand — that the comet left in space on its previous 5.4-year cycles around the sun.

"We hadn't seen that with this comet," said astronomer Michael Kelley, a doctoral student at the University of Minnesota, Twin Cities, and member of the team that made the Spitzer telescope observations. "It's been suspected because it's associated with a meteor shower."

Comet debris streams linked to specific comets, like that seen in the Spitzer image, are the cause of many regular, predictable meteor showers. When Earth plows through the debris at the same point it its orbit each year, the debris burns up in our atmosphere, creating a meteor shower.

The astronomers are hoping that by measuring the brightness of the extent of the debris trail, which can't be see in visible light, they can find out whether most of the comet vaporizes from evaporating ice, the house-sized chunks seen in recent Hubble Space Telescope images, or by way of meteor-sized debris seen in the Spitzer images.

"We suspect that every comet goes through an episode like this," said Kelley of those comets that don't die by plunging into the sun or into a planet.

It's the details that have been elusive, and why Comet 73P/Schwassman-Wachmann 3's break up so conveniently near Earth is getting so much attention.

On Thursday, for instance, some brand new visible light images of the comet from May 3 were released by astronomers who caught the disintegration drama with the 8.2-meter Subaru Telescope in Hawaii.

"Compared to observations five days before by VLT (the Very Large Telescope, in Chile), we see some more parts coming off,” said Catherine Ishida of the National Astronomical Observatory of Japan, which operates the Subaru Telescope on Mauna Kea.

One Subaru close-up of the wake of the comet's "Fragment B" shows distinct miniature comets dropping away in the wake. Thirteen such "mini-comets" have been counted by Subaru astronomers.

Big telescopes will continue to take turns looking at the comet when there is time and until it the comet is too close to the sun for the telescopes to look without damaging their instruments. Each new view tells another part of the story, said Ishida.

"The key thing is that the comet is changing rapidly," she said.