Sky Show This Month: "Two-Tailed" Comet Nearing Earth

Victoria Jaggard
National Geographic News
January 26, 2009

A fresh new face has moved into our neighborhood, but once it swings by Earth next month, it may never come back.

Comet Lulin is currently sailing through the inner solar system and is getting closer to our home planet, with its nearest approach expected in late February.

Although it will probably be hard to see with the naked eye, the 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.

In fact, notes astronomer Mark Hammergren of Chicago's Adler Planetarium, "it's visible right now with a small telescope if you know where to look."

But Hammergren 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 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.

As the object is exposed to the sun's heat for the first time, those ices will vaporize, possibly causing the comet to brighten rapidly or even break apart.

What's more, the comet's orbit is in nearly the same plane as Earth's but 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.

Cosmic 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 sky survey.

Lulin made its closest approach to the sun on January 10, 2009, and has since been getting brighter in the morning sky. Over the coming weeks stargazers will see it move westward from the constellation Libra into Virgo.

Continued on Next Page >>




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