National Geographic News
A newfound comet.

The newfound comet C/2011 L4 (PANSTARRS). Image courtesy Henry Hsieh, PS1

Andrew Fazekas

for National Geographic News

Published June 22, 2011

There's a newfound comet closing in on the sun, and when it gets here in 2013, you may be able to see it with your naked eye.

Astronomers stumbled upon the icy interloper on June 5 while searching for potentially hazardous asteroids.

Equipped with the world's largest digital camera—1,400 megapixels—the University of Hawaii's Pan-STARRS team snagged a faint image of the odd object while it was more than 700 million miles (1.1 billion kilometers) away, between the orbits of Jupiter and Saturn. (Explore an interactive solar system.)

"Almost everything we find is an asteroid, but this object was suspicious," said Richard Wainscoat, co-discoverer of the comet and an astronomer at the University of Hawaii.

"Unlike asteroids, which appear point-like in images, the telltale sign that gave it away was its fuzzy appearance."

(Related: "Weird Asteroid Really a Crusty Old Comet?")

By March 2013 the comet, named C/2011 L4 (PANSTARRS), is expected to come within 30 million miles (48 million kilometers) of the sun—closer even than the innermost planet, Mercury.

When the comet makes its closest approach to the sun, more of its ices will vaporize, adding to its hazy envelope of gas and dust and producing the familiar tail.

This denser envelope, or coma, should boost the comet to peak brightness, making it potentially visible to the naked eye low in the western horizon just after sunset.

Comet a Runaway From the South

While there is no danger of collision with Earth, preliminary calculations of the comet's orbit show that this may be its first and final trip through the solar system.

"It may be coming around the sun for the first and only time, only to be ejected from the solar system, never to return," Wainscoat said.

"Since we don't have a lot of data on it, we really don't know the orbit well enough right now, and it will take up to two months of observations to find out."

Astronomers believe C/2011 L4 may be a runaway from the Oort cloud, a reservoir of billions of hibernating comets that orbits about 100,000 times farther than the distance between Earth and the sun.

"The current path of the comet is typical of those thought to be originating from the Oort cloud, showing it coming up from the south—underneath the Earth—going up the back side of the sun and into the north sky, very nearly perpendicular to the plane of the solar system," Wainscoat said.

The fact that it's going around the back of the sun from our point of view may ultimately affect the comet's visibility, but a lot will depend on how close the body actually gets to the sun.

Also, whether the comet is north or south of the sun when it reaches peak brightness will determine which hemisphere on Earth gets the better view.

(Related: "Comet Is Cosmic Snow Globe, NASA Flyby Shows.")

For now, "we think it will be an easy binocular target, but it may very well make it to naked-eye level, and there is even a potential that it may be visible during the day," Wainscoat said.

"But it's just really too early to tell. We may not know for sure until only a few weeks before it gets here."

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