posted 03-18-2002 10:31 AM            

Scroll down to the third article about the near earth asteroid they didn't see until 4 days after it passed us. It's the quiet ones you have to watch!

posted 03-18-2002 12:35 PM               

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CLOSE ENCOUNTER: On March 8, 2002, a 70-meter wide asteroid glided by Earth only 1.2 times more distant than the Moon. Named 2002 EM7, the space rock approached our planet from the direction of the Sun and was discovered by MIT's LINEAR search program four days after the flyby. Recent observations suggest that the asteroid won't come so close again for at least 100 years.

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posted 03-18-2002 01:02 PM               

Asteroid buzzes Earth from "blind spot"
16:22 15 March 02
NewScientist.com news service

One of the largest asteroids known to have approached the Earth zipped past about 450,000 kilometres away on March 8 - but nobody recorded it until four days later.

The object, now called 2002 EM7, was hard to spot because it was moving outward from the innermost point of its orbit, 87 million km from the Sun. When it passed closest to the Earth - just 1.5 times the distance to the Moon - it was too close to the Sun to be visible.

Asteroids approaching from this blind spot cannot be seen by astronomers. If a previously unknown object passed through this zone on a collision course with Earth, it would not be identified until it was too late for any intervention.

Astronomers have made numerous calls in recent years for more funds to catalogue near-Earth objects and refine their orbits. This would reduce the number of unknown objects that could catch us unaware, and give early warning of potential future collisions.

Bigger than Tunguska

An asteroid-hunting telescope operated by the MIT Lincoln Laboratory first recorded the new asteroid on March 12, as it moved away from the Earth and more of its bright side came into view.

Further observations allowed Timothy Spahr of the Harvard-Smithsonian Center for Astrophysics to calculate its orbit. He found that it has a 323-day orbit that takes it as far as 188 million km from the Sun.

Invisible to the unaided eye, 2002 EM7 is too small to be classed as a "potentially hazardous asteroid". But it is probably between 50 to 100 metres across, making it larger than the object that exploded in 1908 over the Tunguska region of Siberia, flattening trees over 2000 square kilometres.

The approach puts it among the 10 closest known approaches by minor planets, says Brian Marsden of Harvard-Smithsonian. More ominously, only one of the 10 closest objects was larger. This was 1996 JA1, which passed only slightly closer to the Earth on 19 May 1996.

The discovery adds to the list of asteroids which are long shots to hit the Earth in the next century. Preliminary calculations indicate 2002 EM7 has Several chances to hit the Earth in that period, with odds of one in six million to one in a billion, Marsden told New Scientist. Further observations are likely to lengthen the odds.
Jeff Hecht

http://www.newscientist.com/news/news.jsp?id=ns99992052

posted 03-30-2002 09:54 PM               

Fast moving cosmic objects posing threat to earth: Expert

New Delhi, March 22, IRNA -- Comets and asteroids whizzing past earth at supersonic speed pose a potential threat to the existence of the blue planet, eminent astrophysicist Jayant V Narlikar has said callingfor international cooperation to foresee or avert any catastrophic bombardment.

"Calculations have shown that comet Swift Turtle could strike the earth on August 14, 2126. Though none of us would be alive then, the big question remains 'how safe is the earth from such cosmic threats in the near or far future," Narlikar said in Calcutta.

At present the director of the Inter-University Center for Astronomy and Astrophysics, Narlikar said scientists across the world were aware of the threat but averting any eventuality required more coordination between national space programs.

"Though the trajectory of the comet might change due to various gravitational and non-gravitational factors and technology might have evolved manifold by then, the international skywatch program must be strengthened for more vigilance against such dangers", he said.

Citing the example of comet Shoemaker Levy which hit Jupiter in 1994 causing huge damages to planet, he said similar asteroid hits had also been recorded in the past.

posted 06-20-2002 06:40 PM               

Asteroid gives Earth closest shave in years

PARIS (AFP) Jun 20, 2002

A football-pitch-sized asteroid capable of razing a major city came within a whisker of hitting the Earth on June 14, but was only spotted three days later, scientists said Thursday.

Asteroid 2002 MN, estimated at up to 120 metres (yards) long, hurtled by the Earth at a distance of 120,000 kilometers (75,000 miles), well within the orbit of the Moon and just a hair's breadth in galactic terms.

It is the closest recorded near-miss by any asteroid, with the exception of a 10-metre (33-feet) rock, 1994 XM1, which approached within 105,000 kilometers (65,000) miles on December 9, 1994, they said.

"2002 MN is a lightweight among asteroids and incapable of causing damage on a global scale, such as the object associated with the extinction of the dinosaurs," the Near Earth Object (NEO) Information Centre of Britain's National Space Centre said in a press release.

"However, if it had hit the Earth, 2002 MN may have caused local devastation similar to that which occurred in Tunguska, Siberia in 1908, when 2,000 square kilometres (800 square miles) of forest were flattened," it said.

Spokesman Kevin Yates told AFP that the asteroid was only spotted on June 17 -- three days after its flyby.

Had it collided with the Earth, "the most likely thing is that it would have detonated in the atmosphere, creating a blast wave," he said.

"You're talking in the region of 10 megatonnes -- quite a lot of energy to be released in any one place," he said.

The risk of the Earth being hit by an asteroid or comet is very remote, and most objects never come so close as 2002 MN.

NASA's Near-Earth Object (NEO) Program website confirmed the incident and said 2002 MN was spotted by the Lincoln Near Earth Asteroid Research (LINEAR), a project funded by the US Air Force and NASA and located in New Mexico.

The website of the US magazine Sky et Telescope voiced alarm at the near miss.

"What is most shocking is just how close it came to Earth," it said.

"Though the exact details of an impact scenario depend on the rock's composition, had it hit the Earth, the event would have been 'Tunguska-like', with a force rivalling the largest H-bombs."

US and other astronomers are working hard to map large asteroids, greater than a kilometer (five-eighths of a mile) across, that could inflict lasting climate change.

One such monster is believed to have wacked into the Earth 65 million years ago in what is modern-day Mexico, kicking up dust and debris that swathed the planet, unleashing a prolonged winter that ended the long reign of the dinosaurs.

But many specialists are worried that little sustained effort is being made to spot smaller space wanderers, which could still unleash the energy of an arsenal of nuclear bombs if they collided with our home.

In addition, the search for dangerously asteroids is overwhelmingly conducted by telescopes in the northern hemisphere. A rock approaching from the southern hemisphere could go undetected.

Astronomers spot asteroids thanks to the light they reflect from the Sun, which means that smaller ones are frequently only discovered when they are very close to the Earth and become visible.

If one of these were on a collision course, that would leave no time to launch a rocket or missiles to try to deflect or destroy it, or even prepare cities for a potential disaster.

Asteroids are often described as the rubble left over from the building of the Solar System.

They orbit the Sun, but the paths are never eternal, for the trajectories can be deflected by gravitational pull whenever the asteroid passes by a planet or goes around the star itself.

The latest calculations of 2002 MN suggest it has an orbit of 894.9 days and is unlikely ever to be any future threat to the Earth, said Yates.

The next close flyby will be in 2061 but the distance will be much greater than in the June 14 episode, he said.

Asteroids are a very remote yet real peril, because they move at such speeds that they unleash terrific energy on impact.

The Tunguska event was caused by an object estimated to be 60 metresfeet) long. It exploded in the atmosphere with the force of 600 times the Hiroshima bomb.

http://www.spacedaily.com/news/020620121339.dc05vk7l.html

posted 06-21-2002 12:48 AM               

Asteroid detected in a close call with Earth
Thu Jun 20, 4:22 PM ET By THOMAS WAGNER, Associated Press Writer

LONDON - An asteroid the size of a soccer field narrowly missed the Earth by 75,000 miles (120,000 kms) last week, in the closest known approach by objects of this size in decades, scientists said Thursday.

"In the unlikely event the asteroid had struck Earth in a populated area, it would have caused considerable loss of life," said Grant Stokes, the principal investigator for the Lincoln Laboratory Near Earth Asteroid Research Project, whose New Mexico observatory spotted the object. "The energy release would be of the magnitude of a large nuclear weapon."

Another scientist, Brian Marsden of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, said: "It was a close shave."

Marsden, whose organization gathers information on all such encounters, called it "the only object of this size known to have come closer to the Earth than the moon in decades."

The asteroid, provisionally named 2002 MN, was traveling at more than 23,000 mph (38,000 kph) when it was spotted, Stokes said in a telephone interview. It was not detected until three days after it came close to the Earth on June 14. When such asteroids are detected, they are usually spotted when they are approaching or departing Earth.

With a diameter of between 50 and 120 meters (yards), the asteroid was about the size of a soccer field, which tend to be about 105 meters (yards) by 75 meters (yards), Stokes said. The size of asteroids is estimated by measuring their brightness, without knowing their composition.

Although lightweight compared with some asteroids, 2002 MN was big enough to have caused local devastation similar to the impact of one in Siberia in 1908. On that occasion, an asteroid that exploded above Tunguska flattened 2,000 square kilometers (1,240 miles) of forest. The asteroid's air blast was believed to have done the damage, since no crater was found.

In general, damage on the ground depends on what an asteroid is made of, varying from solid metal to a loosely bound aggregate.
"Looking statistically at the asteroid population, maybe 50 times a year a 100-meter-class asteroid passes within a lunar distance of Earth," Stokes said. "But only a handful of such asteroids that have penetrated the Moon's orbit have been spotted by asteroid search programs."

Dr. Benny Peiser, an expert on near earth objects, or NEOs, at Liverpool John Moore's University in England, said: "Whilst the vast majority of NEOs discovered do not come this close, such near misses do highlight the importance of detecting these objects. This reminder comes in a week when the U.K. telescopes on (the Spanish island of) La Palma are being tested to search for NEOs."

Currently, there is no dedicated program searching for NEOs of 2002 MN's size, and the American space agency NASA concentrates its efforts on bodies bigger than one kilometer (.62 of a mile) across.

"NASA has a goal of discovering and obtaining good orbits for all the near earth objects with diameters larger than 1 kilometer," said Thomas Morgan, a scientist at NASA headquarters in Washington. "Asteroids of this size could potentially destroy civilization as we know it."

Asked about the discovery of the smaller 2000 MN asteroid, Stokes said: "We're delighted to have found this object. ... We know objects in this class are not generally detected."

He also said, "It's something the public should know about, but shouldn't get nervous about."

Asteroids of that size are estimated to hit the Earth every 100 to several hundred years, causing local damage, but no disaster to civilization or the planet's ecosystem, Stokes said.

"Civilization has to get used to them on some level," he said, adding that larger ones that NASA is trying to detect and monitor could theoretically hit Earth every million years, or at longer intervals.
(twx/jw)
http://story.news.yahoo.com/news?tmpl=story&u=/ap/20020620/ap_wo _en_po/britain_asteroid_close_call_2&printer=1