Rare Comet Close-Up Coming to a Sky Near You

NASA's Swift Gamma-Ray Explorer satellite took this shot of Comet Lulin on Jan. 28, and regular folks may be able to catch their own glimpse with binoculars on February 23.

The image was taken as the comet was passing through the constellation Libra, 100 million miles from Earth and 115 million miles from the sun. It combines data from Swift's optical and ultraviolet telescope (the blue colors) and its X-ray telescope (red). The star-field background comes from a Digital Sky Survey image.

Lulin's tail — grit and grains from the comet's rock-and-ice surface pushed off into space by solar radiation — extends to the right. Lulin is shedding 800 gallons of water every second, according to NASA astronomers. That's enough to fill an Olympic-size swimming pool in less than 15 minutes.

Solar radiation also breaks comet water down into hydroxyl particles, composed of one oxygen and one hydrogen atom. Swift determined that the hydroxyl cloud around Lulin is about 250,000 miles wide, slightly greater than the distance from the Earth to the moon.

Lulin, discovered in July 2007, is now visible to the naked eye in dark, rural skies. But the view will get better: On the night of Feb. 23, Lulin will pass within 38 million miles of Earth, appearing about 2 degrees south-southwest of Saturn in the night sky. Stargazers with binoculars should get a good look. By mid-March, Lulin will have zoomed off into deep space and out of sight.