Jimmy Westlake: Catch Comet SWAN

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Get ready, comet lovers! A new comet has been discovered in photographs taken by the SWAN camera onboard the SOHO spacecraft and should give sky watchers their first comet visible in binoculars since Comet Schwassmann-Wachmann 3 in May 2006.

SOHO, or the Solar and Heliospheric Observatory, is a satellite operated jointly by NASA and the European Space Agency. It orbits the Sun near the gravitationally stable L1 point of the Earth's orbit, about 1-million miles inward from Earth toward the Sun. SOHO and its SWAN camera have discovered dozens of comets in the last decade, most of which never made it to the level of naked-eye visibility. Comet SWAN, as it is called, might become faintly visible to the unaided eye during October and November, but it will certainly be an easy binocular object in dark skies.

Comets are like big, dirty snowballs, more than anything else, that hover near the outer edges of the solar system where they exist in perpetual cold and dark. Every so often, one of these frozen snowballs falls into the inner solar system where the warmth of the Sun begins to vaporize the icy material and release thousands of little dust grains. The pressure of the sunlight and the solar wind blows this gas and dust away from the comet's head forming the beautifully eerie tail for which comets are named. The word comet comes from the Greek word kometes, meaning "hairy star."

Comet SWAN is visible now near the handle of the Big Dipper. If you own a pair of ordinary binoculars, try scanning the area underneath the Big Dipper's handle near the star Cor Caroli in the northwestern sky as soon as it gets dark in the evening. Comet SWAN will be right beside the star Cor Coroli on the evenings of October 7 and 8, but the bright, full Harvest Moon will make observing difficult. You might have better luck seeing the comet a few nights later when the Moon is out of the way and the comet is closer to the star Alkaid at the end of the Big Dipper's handle. Be sure that you have an unobstructed view of the northwestern horizon.

For a few nights around Halloween, Comet SWAN will be in the same binocular field with the Great Hercules Star Cluster, M13, and by Thanksgiving, will be situated near the bright star Altair. By then, however, the comet will be on its way out of the inner solar system and will have faded substantially.

To see a beautiful photo of Comet SWAN, visit NASA's "Astronomy Picture of the Day" website at this address: http://antwrp.gsfc.nasa.gov/apod/ap061004.html.

Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the websites of CNN.com, NASA's "Astronomy Picture of the Day," Spaceweather.com, Space.com, Discover.com, and in Sky & Telescope, Astronomy, Night Sky, Discover, and WeatherWise magazines. His "Celestial News" article appears weekly in the local Steamboat Pilot newspaper. He also records a radio spot for the local stations KFMU and KRMR called the "Cosmic Moment."

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