A fresh new face has moved into our neighborhood, but once this green comet swings by Earth early Tuesday, it may never come back (picture of green comet Lulin).
Comet Lulin is currently sailing through the inner solar system and is getting closer to our home planet, with its nearest approach expected before dawn on February 24.
Although it's hard to see with the naked eye, the green-colored comet "should be a fairly easy object [to see with] modest amateur telescopes or even binoculars," said Don Yeomans, a comet expert at NASA's Jet Propulsion Laboratory in Pasadena, California.
Astronomer Mark Hammergren of Chicago's Adler Planetarium notes that the icy body has the potential to do something unexpected.
Comet Lulin is arriving from the far reaches of the solar system on a nearly parabolic orbit—"it's almost as if it comes from infinity and goes back out to infinity," he said. (Explore an interactive solar system.)
This means comet Lulin could be on its first pass by the sun, so the comet should still be encrusted in "fresh" ices preserved by the freezing environment of the outer solar system, Hammergren said.
As Lulin is exposed to the sun's heat for the first time, those ices are vaporizing—activity that could cause the comet to brighten rapidly or even break apart. Even now the comet is spewing cyanogen and diatomic carbon, both gases that glow green in sunlight out in the vacuum of space.
What's more, the green comet's orbit is in nearly the same plane as Earth's but the comet is traveling in the opposite direction. This causes Lulin to appear to move unusually fast and display a rare anti-tail—an optical effect that creates a secondary "tail" pointing toward the sun.
Green Comet Fuzz Ball
Quanzhi Ye, a student at China's Sun Yat-sen University, found comet Lulin in 2007 while examining images from the Lulin Observatory in Taiwan as part of an asteroid survey.
Lulin made its closest approach to the sun on January 10, 2009, and has since been getting brighter in the morning sky.
Close to dawn on Tueday, the comet will pass nearest to Earth—about 38 million miles (61 million kilometers) away—and will reach peak brightness and fastest apparent speed.
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