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Mountain-Size Asteroid Will Whip Past Earth on Monday

Asteroid 2004 BL86 will come within 745,000 miles of our planet — about three times the distance between Earth and the moon.
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A mountain-size asteroid will zoom past Earth Monday (Jan. 26), marking the closest pass by such a large space rock until 2027.

Asteroid 2004 BL86, which is about 1,800 feet (550 meters) wide, will come within 745,000 miles (1.2 million kilometers) of our planet Monday — about three times the distance between Earth and the moon. While this flyby poses no threat to Earth, it does present a rare opportunity to get a good look at a near-Earth asteroid, NASA officials say.

Scientists are eager to study 2004 BL86 to pinpoint its orbit, observe its surface and even look for moons. The plan is to track the fast-moving asteroid using the 230-foot (70 m) dish-shaped Goldstone antenna at NASA's Deep Space Network in California, as well as the 1,000-foot (305 m) Arecibo Observatory in Puerto Rico. These radio dishes will beam microwave signals at the asteroid, which will then bounce off the target and return to Earth. [Photos: Potentially Dangerous Asteroids]

Image: Artist’s concept of an asteroid flying close to Earth
An artist’s concept of a near-Earth asteroid flying close to Earth.ESA / P. Carril

"For objects that get this close, that are this large, the radar observations are really analogous to a spacecraft flyby in terms of the caliber of the data that we can get," said Lance Benner of NASA's Jet Propulsion Laboratory in Pasadena, California, who is the principal investigator for the Goldstone observations of the asteroid.

The resulting black-and-white images can reveal unprecedented details about asteroids, whereas most ground-based telescopes would see only a point of light. But the first item on the team's checklist will be to nail the space rock's location in space and time. This will enable a better understanding of the object's orbit and its future motion, scientists say.

Even though 2004 BL86 poses no threat to Earth for the foreseeable future, it's still a good idea to keep a close eye on the asteroid, Benner said.

"Really, it's an inexpensive form of insurance to monitor these objects on a regular basis," he told

You can watch 2004 BL86's flyby in visible light (as opposed to radar observations) live online Monday via the Virtual Telescope Project in Italy.

— Shannon Hall,

This is a condensed version of a report from Read the full report. Follow Shannon Hall on Twitter @ShannonWHall. Follow @Spacedotcom, Facebook and Google+.