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Planetary News: Near Earth Objects (2006)

Astronomers Gearing Up to Observe Fast-Moving Visitor

30 June, 2006

Amateur astronomers equipped with medium sized telescopes will be treated to a remarkable display on the night of July 2-3, as a visiting space rock will zoom by Earth at a dazzling speed. The rock, also known as asteroid 2004 XP14, is a member of the nearly 200 strong "Apollo" family of asteroids, whose orbits intersect Earth's. It will make its closest approach at 4:25 am on July 3, Universal Time (9:25 pm on July 2, Pacific Daylight Time), passing at a distance of 432,617 kilometers (268,873 miles ) from Earth -- just 10% greater than the average distance of the Moon.

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At its brightest, the asteroid will reach the 11th magnitude, making it visible with telescopes of 8 inch apertures or more. Speeding along at 17 kilometers per second (10.5 miles per second), the asteroid will be moving by so fast that it will be covering 8.323 degrees every hour. This is equivalent to the diameter of the Moon every four minutes! With the proper equipment, observers will actually be able to see 2004 XP14 move across the sky.

The precise size of 2004 XP14 is not known, but based on its brightness astronomers estimate it to be between 400 and 900 meters (1300 to 3000 feet). This would mean a good-sized impact if the asteroid ever strayed into Earth's path, and indeed when 2004 XP14 was first discovered there was some concern that it might be on a collision course with  Earth later in the century. Further calculations have since made it clear that a collision is, in fact extremely unlikely.

Asteroid 4179 Toutatis
Click to enlarge >
Asteroid 4179 Toutatis
Radar view of Toutatis captured using the Goldstone radio telescope. Source Credit: Image ©1995 AAAS, courtesy Steven Ostro

Nevertheless, NASA scientists want to learn as much as possible about this fast-moving neighbor by pinging it with radar signals as it flies by. On the nights of July 3, 4, and 6, they will point the giant 70 meter (230 foot) radio telescope at Goldstone, California, at the asteroid, and bounce high-frequency radio signals off its surface. From this they hope to learn 2004 XP14's exact orbit, mapo its shape, and get good indications of its mass and density. Because of the asteroid's size and it close pass of Earth, it will be the strongest asteroid radar target of all time.

"Close flybys of Earth like this one, or the even closer flyby the asteroid Apophis will make in 2029, remind us that we live in a cosmic shooting gallery," said Bruce Betts, Director of Projects for The Planetary Society. "We must be vigilant in our efforts to find potential impactors, and in our ponderings of what to do if one is coming for Earth," he added.