FLASH! Meteor to Explode Tonight

Saw that coming. Astronomers for the first time have predicted the arrival of a meteor like this one.

Credit: V. Winter & J. Dudley/ICSTARS Astronomy

By Richard A. Kerr
ScienceNOW Daily News
6 October 2008

Astronomers scanning the skies for asteroids that could hit Earth have found one, and it won't be long getting here. Near-Earth object (NEO) 8TA9D69 will strike the atmosphere over Sudan tonight at 0246 UTC, 5:46 a.m. local time, according to calculations by celestial dynamicist Steven Chesley of NASA's Jet Propulsion Laboratory in Pasadena, California.

Not to worry. Despite packing a punch equivalent to 1000 tons of TNT, the approximate 2-meter-diameter rock-- discovered last night during a sky-survey program conducted by the University of Arizona's Mt. Lemmon Observatory--will break up in the atmosphere in a fiery display called a bolide. "The damage on the ground is expected to be zero," writes astronomer Andrea Milan of the University of Pisa in Italy, on the Minor Planet Mailing List run for asteroid and comet researchers (groups.yahoo.com/group/mpml/).

"This is the first time an asteroid impact has been predicted," writes planetary astronomer David Morrison in his NEO News e-mail newsletter. The discovery reflects the increasing capability of the worldwide watch for NEOs, he says, which in this case was smoothly coordinated through the International Astronomical Union's Minor Planet Center in Cambridge, Massachusetts. For the first time, humans need not look up in surprise at a bit of out-there falling down here.

Caught. An ultra-low-frequency sound detector recorded the signal (tall line between 400 and 500 seconds) of the asteroid blasting through the atmosphere.

Credit: P. Brown/University of Western Ontario

Asteroid Watchers Score a Hit

By Richard A. Kerr
ScienceNOW Daily News
8 October 2008

Two days ago, Science reported that astronomers were predicting an asteroid impact for the first time (ScienceNOW, 6 October). Chalk one up for the astronomers. "The prediction clearly was correct," says planetary scientist David Morrison of NASA's Ames Research Center in Mountain View, California.

First detected on 5 October at the University of Arizona's Mt. Lemmon Observatory, the asteroid was calculated to enter the atmosphere over Sudan early on the morning of 7 October, erupting into a fireball in the sky but not damaging the ground. Although no sightings of the 2- to 3-meter-diameter rock burning itself up have come in from the ground, two other sorts of detections--one human and one instrumental--were made. Aviation meteorologist Jacob Kuiper of the National Weather Service in the Netherlands alerted KLM airliner pilots to the opportunity, and one flying 750 kilometers southwest of the predicted arrival spot reported a short flash just before the predicted time and in the predicted direction.

A ground instrument installed in Kenya to detect the extremely low-frequency sound waves of nuclear explosions recorded a signal generated 2 minutes before the prediction (see image), according to meteor specialist Peter Brown of the University of Western Ontario in London, Canada. To generate that signal, an extraterrestrial object would have needed to arrive from the predicted direction and with roughly the predicted energy, Brown calculates.

"I think we can be pleased with how this was handled on an international basis," says Morrison. Astronomers around the world were exchanging observations and impact predictions in near real time, he says, with NASA headquarters in the loop. He doesn't know whether anyone let the Sudanese know what was about to happen.

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FLASH! Meteor to Explode Tonight

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