Press Release

Subaru Captures Crumbling Comet Schwassmann-Wachmann 3

May 11, 2006

Comets within a Comet (Enlarge)

The Subaru Telescope on Mauna Kea has captured an image of the comet Schwassmann-Wachmann 3 as its nucleus continues to crumble into more than fifty pieces. Subaru observed one of these icy chunks, called Fragment B, on May 3, 2006, using the telescope's wide-field camera Suprime-Cam as the comet passed within 16.5 million kilometers (just over 10 million miles) from Earth. (This is about 41 times the distance between Earth and the Moon.) The resulting visible-light image shows gas and dust forming the characteristic shape of a comet, with a halo-like coma and dust tail around Fragment B. Amazingly, it also reveals at least thirteen mini-comets that have recently broken off from the fragment. This is five mini-comets more than the number found in observations on April 23, 2006 by the European Southern Observatory's VLT (Very Large Telescope) in Chile.

A detailed analysis of the cometary fragments is yet to come. However astronomers have determined that the small pieces are only several tens of kilometers in diameter and are likely to disappear in a short time. Exactly how short is one of the questions astronomers are hoping to answer. Tetsuharu Fuse from Subaru Telescope says "the combination of information from many telescopes including large telescopes like Subaru and the VLT and smaller telescopes like the Ishigakijima Astronomical Observatory in Okinawa, Japan, will give us the insight into how comets fall apart and conversely how they hold together."

Comets are often described as "dirty snowballs," loose clumps of dust and ice covered by a crust of dirt. As they approach the Sun, comets can warm up and fall apart. In 1995, astronomers saw this comet become a thousand times brighter, and found that its nucleus had broken into three pieces. This year, observations from around the world have confirmed that the nucleus has broken into more than 50 pieces.

Friedrich Carl Arnold Schwassmann and Arno Arthur Wachmann from Germany discovered the comet, which is formally called 73P/Schwassmann-Wachmann 3, in 1930. It travels around the Sun in an 5.4-year-long elliptical orbit . When the comet approaches the Sun, depending on where Earth is in its orbit, the comet may or may not pass near us. Schwassmann-Wachmann 3 was long known as a "mystery comet" because it had been lost to observers for 50 years before it was rediscovered in 1979.

Over the next week, the comet will pass by Earth at a distance of 12 million kilometers (about 7.5 million miles). This is about 30 times the distance between Earth and the Moon. Astronomers are keeping the giant eyes of telescopes pointed at this comet, and at the Subaru telescope, infrared light observations have already taken place.

People with binoculars or small telescopes can also see the brightest fragments of the comet as they pass through the constellations Cygnus and Pegasus over the next week. Viewing will probably be best after May 18th, when moonlight will not outshine the comet. Observers wishing to track the comet can look for finder charts searching the World Wide Web with the keywords "comet 73P chart" or going to most major astronomy web sites.

From Hawai'i, the best time to observe the comet is in the morning before sunrise. The comet will be high overhead in the northeastern sky over the next week.

Subaru is an 8.2 meter optical-infrared telescope on Mauna Kea, Hawaii, operated by the National Astronomical Observatory of Japan, a member institute of Japan's National Institutes of Natural Science.

The research team: Tetsuharu Fuse, Subaru Telescope, National Astronomical Observatory of Japan (NAOJ). Hisanori Furusawa, Subaru Telescope, NAOJ. Junichi Watanabe, NAOJ. Daisuke Kinoshita, Taiwan National Central University. Naotaka Yamamoto, Grid Technology Research Center, National Institute of Advanced Industrial Science and Technology, Japan

Object: Comet 73P/Schwassmann-Wachmann 3 Fragment B
Telescope and Focus: Subaru Telescope Prime Focus
Instrument: Suprime-Cam
Filter: R-band (0.65 micrometers)
Observation Time: May 3, 2006, UT
Exposure Time: 8 minutes
Field of View: Approximately 32.5 arcminutes x 23 arcminutes (Insert: 1.5 arcminute x 1 arcminute)
Orientation: North is up. East is left.

Finding chart for the brightest fragment of Comet Schwassmann-Wachmann 3 (Fragment C) for May 12 though May 20, 2006. (Larger Image)

Mini-comets that have broken off from Fragment B of Comet 73P/ Schwassmann-Wachmann 3. The main body of Fragment B is the bright  object in the upper left corner. (Larger Image)

Comet 73P/Schwassmann-Wachmann 3, Fragment B (Larger Image)

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