1st Potentially Hazardous Asteroid Sighted by NEO Warning System

Pan_starrs The Panoramic Survey Telescope & Rapid Response System instrument on the summit of Haleakala on Maui, Hawaii, has discovered an asteroid that will come within 4 million miles of Earth in mid-October, a release by the Harvard-Smithsonian Center for Astrophysics said. It is the first "potentially hazardous object" (PHO) to be discovered by the Pan-STARRS survey and has been given the designation "2010 ST3."

The asteroid is about 150 feet in diameter and was photographed Sept. 16 when it was about 20 million miles away, the release said.

"Although this particular object won't hit Earth in the immediate future, its discovery shows that Pan-STARRS is now the most sensitive system dedicated to discovering potentially dangerous asteroids," Robert Jedicke of the University of Hawaii said. "This object was discovered when it was too far away to be detected by other asteroid surveys."

Although most of the largest PHOs have already been catalogued, scientists suspect there are many more under a mile across that have not yet been discovered, and that could cause devastation on a regional scale if they ever hit our planet.

“On a daily basis, we’re hit with basketball-sized objects, and Volkswagen-sized objects come in a few times a year,” says Dr. Donald K. Yeomans, who heads NASA’s Near Earth Object (NEO) Program Office, which continues to spearhead the global effort to identify and track significantly large asteroids in near-Earth space. “Fortunately, the limiting size for something that will actually do ground damage is about 30 meters [98 feet], and you’d expect something like that to come in every 200 years or so on average.”

That directive includes rocks more than a kilometer (0.6 miles) across, which typically hit the Earth in million-year intervals. These asteroids are capable of causing global consequences. Larger objects, including the ten kilometer “dinosaur killer” that occurred 65 million years ago, are capable of plunging the globe into apocalyptic winters that last for years. Fortunately, these large object impacts hit Earth at intervals in the tens of millions of years.

“Asteroid size has this interesting distribution where there are very few of the big ones,” says Lowell Observatory research scientist Bruce Koehn. “The smaller the size, the more there are.”

.“We’ve discovered almost 90 percent of the total population of NEOs larger than a kilometer, and none of them are a threat,” Yeomans says. “So the next step is to extend the survey down to 140 meters [459 feet], which Congress has asked NASA to handle. That will take larger, wider field telescopes, which hopefully will come on line within a few years. Actually one of them is already on line, the Pan-STARRS telescope on Maui.”

“When our project started in the late ’90s, the risk of dying from an asteroid impact was approximately the same as dying from an airplane crash,” says Koehn. “Twelve years of near-Earth asteroid surveys have reduced the risk simply by increasing our knowledge. So the risk of being hit by something we haven’t found is 10 times less than it was.”

We’ll never completely find every object that has an Earth-threatening trajectory,” Yeomans says. “Some of them are quite small and difficult to find till they’re almost upon us.”

Plus as Bruce Koehn points out, “Orbits change. They change due to interactions with major planets and large asteroids. They change because of [close approaches between asteroids] and for a variety of other reasons. So while we know whether most of these asteroids are coming near the Earth, we don’t know the details of these interactions because we don’t know the orbits well enough to calculate these close approaches. So there is kind of a fundamental level beyond which we cannot know, and we’ll always have that level of risk.”

“The asteroids in the most Earth-like orbit are the ones that threaten us most, but they’re also the ones that are easiest to get to,” Yeomans says. “The Obama administration has said that the next human space flight target is likely an asteroid, so these near-Earth asteroids are not only a threat, but they’re opportunities for exploration and future space resources.”

Via UPI upi.com/Science_News and http://blog.cytalk.com

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