Astronomer says threat from asteroid 'minimal'

A large and newly sighted asteroid is reported to be on a potential collision course with Earth in 2019. Astronomers said last week, those observations are scary but not necessarily accurate.

For now they're watching and waiting.

The existence of the asteroid was reported by the British Broadcasting Corp. Astronomer Donald Yoemans, from the Jet Propulsion Laboratory in Pasadena, Calif., told the BBC that "the threat is minimal" despite calculations showing the asteroid known as 2002 NT7 might hit on Feb. 1, 2019.

The 1.2-mile-wide asteroid was discovered July 9 by LINEAR, the Lincoln Near Earth Asteroid Research Project, using a telescope near Socorro, N.M. The program is run by the Massachusetts Institute of Technology's Lincoln Laboratory.

Scientists estimated Wednesday that the big rock has slightly less than a one-in-a-million chance of colliding with Earth -- one of many scenarios.

Astronomer Gareth Williams, at the International Astronomical Union's central telegram bureau in Cambridge, Mass., said it's probable the risk "will go away when we have observed it for a longer period of time." But if it were to collide with Earth, we should plan for a very, very long winter.

Williams estimated that if 2002 NT7 were to hit, the event would equal a blast comparable to about 1 million megatons of TNT, far larger than any man-made explosion.

Nevertheless, "I'm not particularly fazed by" the prediction, he said. "I will not start getting worried until it turns out this thing is not going away."

Continuing observation

Astronomers have given asteroid 2002 NT7 a rating of "1" on the Torino impact hazard scale, meaning it is an object worthy of careful monitoring. Observations will continue into next year to ascertain its true orbital path as it cruises around the sun every 837 days. A collision could occur if its path intersected Earth's orbit.

In any case, Williams said, "what's unusual about this is that it is so big -- it's 2 kilometers across -- and we really don't want a 2-kilometer object falling onto the Earth."

Statistically, every 100 million years a 6-mile-wide object hits the Earth with an impact similar to the one that most scientists believe wiped out the dinosaurs 65 million years ago.

Williams said reports of this kind seem scary at first because they're premature -- too soon for the asteroid's true orbit to be calculated with precision. Later, when refined figures show no likelihood of impact, it's just "ho hum," he said.

The problem, of course, is that even a small chance of impact is scary. Geological evidence makes it clear that major impacts have occurred in the past, sometimes causing damage on a global scale.