This asteroid is estimated from its brightness to be roughly 300 m in diameter -- about the size of the largest shopping center (including the parking lots). Its distance of closest approach is about twice the distance of the Moon from the Earth. YB5 was discovered on December 26 by the NEAT survey team at Palomar Mountain.
YB5 is classed as "potentially hazardous" because its orbit brings it so close to the Earth. However, there is no danger of it hitting our planet on any future pass for at least the next several centuries. If it ever does hit our planet, an asteroid of this size would excavate a crater (on land) the size of a small city, and the blast would cause considerable damage on the scale of a country like France. Fortunately, asteroids this size collide with Earth only at average intervals of about 20,000 - 30,000 years. However, something as big as YB5 comes as close as this roughly annually. Thus many thousands of objects come close (a "near miss") for every one that actually hits. Most of these are undetected, since the coverage of the Spaceguard Survey is limited for asteroids this small and faint.
Following are several international news stories that describe the flyby of YB5 in further detail, although most to them quote impact frequencies that are probably too high according to our current understanding of the population of the near Earth asteroids.
David Morrison
EARTH ESCAPES BRUSH WITH KILLER ASTEROID
From CNN, 7 January 2002
By Richard Stenger
CNN Sci-Tech
(CNN) -- An asteroid that could pulverize a country zipped close by the Earth on Monday, only weeks after astronomers first noticed the big space boulder heading in our direction. The Near Earth Object brightened enough for even simple telescopes to spot just before it raced past our planet on Monday, only two times the distance of the moon, according to spaceweather.com, a NASA-affiliated Web site.
The range might seem like enough to breath easy, about 600,000 km (375,000 miles), but many scientists classify it as a relatively close call. The asteroid, officially known as 2001 YB5, measures between 300 and 400 meters (1000 to 1300 feet) in width. If such a rock were to smash into the planet, it would unleash the same amount of energy as many nuclear bombs, astronomers estimate.
"The impact would be quite tremendous. It could essentially wipe out a medium-sized country," said Benny Peiser of the Royal Astronomical Society in Great Britain. "The environmental consequences would be regional but the social and economic consequences would be global."
Close encounters with giant space rocks are not uncommon. Asteroids comparable to 2001 YB5 could strike the Earth as frequently as once every 5,000 years, Peiser said. The space rock 2001 YB5, identified by the arrow, could have wiped out France, according to a scientist in Britain.
In much rarer instances, boulders one kilometer or greater in size have smacked into the planet and snuffed out most life forms, much like the six-mile (10-km) long monster thought to have forced dinosaurs to exit stage left about 65 million years ago, according to scientists.
In the year 2027, an asteroid between one kilometer and mile in length is expected pass even closer than 2001 YB5. Having pinpointed its orbital path, scientists dismissed any potential of danger. But later on, either asteroid could pose risks to the planet, along with countless rocks lurking in the shadows that have yet to be identified, astronomers warn.
What particularly troubles Peiser is that scientists only first spotted 2001 YB5 in early December. What if it had been heading on a collision course? "That's not enough time for any initiatives for deflection. If we had 20 or 30 years' time, then we could develop a technology to deflect an object. With our current lacked of preparedness, we are helpless," he said.
Copyright 2002, CNN
MONSTER FROM OUTER SPACE JUST MISSED US
From The Age, 9 January 2002
By DAVID WROE
An asteroid big enough to obliterate a major country missed Earth by a stellar hair's breadth on Monday night, prompting calls from scientists for Australia to join the search for rogue space rocks.
Had it struck, the asteroid, measuring up to half a kilometre across in places, would have created the force of hundreds of atomic bombs. Instead, it glided harmlessly past less than twice the distance from the moon to Earth, coming within 600,000 kilometres at 6.37pm on Monday.
In astronomical terms it grazed the Earth's surface, said Brian Schmidt, Australian National University's expert on asteroids. Had it hit metropolitan Melbourne it would have created total devastation for 150 kilometres, and taken out most of Sydney as well. "Such an object would literally wipe out a medium-sized country and lead to a global economic meltdown," said Benny Peiser, an asteroid expert from John Moores University, in England.
The asteroid, named 2001 YB5, was spotted early last month by a Near-Earth Asteroid Tracking (NEAT) survey telescope on Mount Palomar, California. But asteroids larger than 2001 YB5 frequently passed near Earth without being noticed, said Australian physicist Paul Davies.
An asteroid one kilometre across could destroy half the world's population, creating a cataclysmic shockwave and tsunamis, followed by a hurricane and an earthquake that would topple buildings around the globe. "You're talking about something pretty colossal," he said.
Apocalyptic asteroids such as the massive hunk of rock 10 kilometres wide that wiped out the dinosaurs 65 million years ago, are rare occurences. But impacts such as the 60- metre asteroid that hit Siberia in 1908, with a force 600 times that of the Hiroshima bomb, happened once or twice every century, Professor Davies said.
There would be virtually no warning, but with more money worldwide for the NEAT program, scientists could spot a rogue asteroid well in advance, giving military specialists enough time to knock it off its path with controlled nuclear missile strikes.
Australia had an asteroid-spotting program partly funded by the Federal Government, but this was stopped by the Howard Government in 1996. It would cost only several million dollars a year to fund the search, Professor Davies said. The US and Britain were keeping watch, but in the southern hemisphere, Australia was letting the world down, he said.
A spokeswoman for Science Minister Peter McGauran said he would investigate funding a program, and Dr Schmidt said he hoped to soon start his own asteroid watch.
Copyright 2002, The Age
ASTEROID MISSES EARTH BY A COSMIC WHISKER
From National Post Online, 8 January 2002
Asteroid misses Earth by a cosmic whisker. Devastation averted: B.C. program
that tracks space rocks just lost funding
Margaret Munro and Joe Brean
National Post, with files from Agence France-Presse
Between 20,000 and 50,000 years ago, a small asteroid about 24 metres in diameter struck the Earth and formed this crater in Arizona that measures 1.2 km in diameter. The discovery of fragments of the Canyon Diablo meteorite helped prove the feature was in fact an impact crater.
An asteroid packing the power of hundreds of nuclear bombs and capable of wiping out a major country hurtled past Earth early yesterday in what astronomers say was a close call. The giant space rock, known as 2001 YB5 and believed to be between 220 and 490 metres across, was only twice as far away as the moon as it sped by Earth at about 1:30 a.m. Eastern time.
Experts said the distance -- about 600,000 kilometres -- is a whisker in cosmic terms, and the rock would have caused global chaos had it smacked the planet.
"It could have vaporized the core of a city like Toronto, leaving a crater two to three kilometres across and creating a huge fireball and shock wave that would have knocked you off your feet in Vancouver," says University of Victoria astronomer Dave Balam, who has been tracking asteroids for 25 years.
He and other astronomers say the dust cloud kicked up by such an impact could have exacted a huge global toll, triggering crop failures and climate changes that could have been felt for years. "Such an object could literally wipe out a medium-sized country if it impacted and lead to a global economic meltdown," said British asteroid expert Benny Peiser, at Liverpool John Moores University.
Even worse, the asteroid could have crashed into the ocean, unleashing devastating tsunamis. Had YB5 splashed down in the Pacific, low-lying coastal cities and communities from Canada to Australia could have been hit, causing millions of deaths, says Professor Peter Brown at the University of Western Ontario, who studies such space menaces.
While asteroid YB5 is now safely past Earth, Prof. Brown and other scientists say the fly-by is a reminder of how vulnerable the planet is to the huge wayward rocks that periodically come flying out of the asteroid belt between Mars and Jupiter. Thousands of asteroids the size of YB5 are believed to be flying though space but there is little information on their orbits, Prof. Brown said. As in the case of YB5, they just suddenly appear on the radar screen.
YB5 was only spotted heading toward Earth on Boxing Day by a Near-Earth Asteroid Tracking survey telescope on Mount Palomar in California. NASA designated the asteroid "potentially hazardous," a designation that applies to any object larger than 150 metres that will come within 7.5 million kilometres of our planet, says Don Yeomans, manager of NASA's Near Earth Object Program office.
By studying the light reflecting off the rock, scientists estimate it is travelling at 30.6 kilometres a second. If it hit, Mr. Yeomans says, the impact would have weighed in at 6,000 megatonnes.
Astronomers stress that at no point did they think the asteroid would crash into Earth -- a good thing, as there was too little time to have done anything to deflect or destroy the asteroid. "It is a reminder of what is going to happen unless we track them more efficiently than we do and make better preparations to defend our planet," Dr. Peiser said.
U.S. and British astronomers have been improving efforts to track potentially hazardous asteroids. But a key component of the international effort -- Mr. Balam's asteroid- tracking program in Victoria -- was shut down three weeks ago because of a lack of funding and support. "We just couldn't keep it up," says Mr. Balam, noting how the program operated on a shoestring budget for years.
The National Research Council contributed time on its telescope in Victoria more than 100 nights a year, and a U.S. foundation had been covering Mr. Balam's salary as he tracked small asteroids and fed the information to the international asteroid tracking community. The U.S. funding was cut last year and no Canadian money could be found to replace it, despite an endorsement from the Canadian Space Agency's meteorites and impacts advisory committee, which wanted the program to survive.
"It's really an incredible loss to Canadian planetary science, and a big loss to the international community," says Prof. Brown, who sits on the committee. He says Mr. Balam is one of the world's premier asteroid trackers. "People like Dave are a national treasure," said Prof. Alan Hildebrand, at the University of Calgary, who chairs the CSA committee.
Astronomers are becoming increasingly vocal about the risks of asteroid collision, saying Earth has simply had a long run of good luck in escaping big cosmic debris. NASA's main focus is on identifying asteroids between one and 10 kilometres across. The number of these is estimated at 700 [more likely 1000], plus or minus 230 [we have already found more than 700-230=470!]. That leaves the vast majority of space objects, which are under one kilometre, still to be detected and tracked.
An asteroid believed to be about 10 kilometres across smashed into Mexico's Yucatan Peninsula 65 million years ago, killing the dinosaurs and much other life on Earth. That impact is believed to have triggered a firestorm and a dust cloud that obscured sunlight around the planet for decades. The space rock that flew by yesterday was "not in the same game," said Prof. Hildebrand, who helped prove a giant asteroid killed off the dinosaurs. But Prof. Hildebrand says smaller rocks -- like 2001 YB5 -- pose a real threat and should be tracked, since it might be possible to divert those bound for Earth.
In 1908, an asteroid believed to have been about 60 metres across exploded over Siberia with the force of 600 times the Hiroshima bomb, reducing a 40-kilometre wide patch of forest to matchwood.
David Jewitt, an astronomer at the University of Hawaii at Honolulu, has estimated there is a 1% chance the Earth will be struck by a 300-metre asteroid sometime this century. "Such an impact would deliver a withering 1,000- megatonne explosion and cause perhaps 100,000 deaths," he said, adding that in a densely populated area, such as the U.S. eastern seaboard or Western Europe, the fatalities could rise into tens of millions.
Copyright © 2002 National Post Online
EARTH ESCAPES CLOSE CALL WITH MASSIVE ASTEROID
From FLORIDA TODAY, 8 January 2002
By Steven Siceloff
CAPE CANAVERAL -- An asteroid the size of a city block [actually, several city blocks] passed Earth on Monday, reminding astronomers of the risk posed by thousands of objects that could slam into the planet with little warning.
The asteroid, named 2001 YB5, approached less than 520,000 miles from the Earth -- about twice the distance from the Earth to the moon. That is a close call to astronomers who discovered the object only two weeks ago.
Longer than three football fields, the asteroid would've doomed any state it landed on or drowned coastal cities in a tidal wave in the event of an ocean impact, experts said. "It would be well beyond all of the atomic weapons in the U.S. and Russian arsenals," said Don Yeomans, project manager of NASA's Near Earth Objects program. "If it hit in the ocean near a continent, all the cities on that coast would be destroyed."
An asteroid the size of YB5 does not carry enough energy to wipe out life worldwide, said David Morrison, who analyzes asteroid and comet impacts at NASA's Ames Research Center in California. But it would cause problems. "The impact of something that big would dig an impact crater the size of Melbourne and do damage for several states around," he said. "If I'm in San Francisco, I would not be affected if it hit in Florida." Asteroids of that size hit Earth about once every [10,000 - 20,000] years, Morrison said.
The asteroid that passed by Monday travels 19 miles a second, offering little time to move it out of the way -- even if that were possible -- if it threatened Earth. "By the time you found it, you wouldn't be able to do anything," said Bob Farquar of Johns Hopkins University Applied Physics Laboratory. Farquar led the Near Earth Asteroid Rendezvous program that landed a satellite on an asteroid last year.
Farquar said officials may try to use missiles against an approaching rock out of desperation, but said it could be a waste since scientists know so little about the makeup of the objects.
"There's nothing you could have done in two weeks," Morrison said. "Nor even two years." Morrison said it would take years if not a decade or more to assemble a rocket and components needed to nudge a doomsday asteroid away from Earth. "This is the one natural disaster we could do something about," he said. "I doubt we'll ever be able to invent a machine that can stop an earthquake."
Objects larger than a mile across are estimated to crash into Earth about once every million years, according to Morrison. There are perhaps 100,000 objects similar to YB5, Yeomans said. Astronomers have found about 1,000 of them so far. More than 350 of the objects have been labeled potential threats to Earth. NASA has given the near earth object program the goal of finding 90 percent of objects two-thirds of a mile or larger that fly near Earth by 2008.
While the odds of substantial asteroids hitting the Earth are small, the consequences are too severe to risk doing nothing, Yeomans said. "The key is to find these things decades in advance, then you can track them and predict when they might hit Earth," Yeomans said. "This is Mother Nature's way of giving us a wake-up call."
While some are concerned the asteroid was found less than a month before its closest swing by Earth, Morrison took it as a good sign that astronomers are getting the equipment they need to find the asteroids. "Something that big goes by the planet that close every few months, we just happened to find this one," he said.
NASA and its staff of a few dozen astronomers spend $3.5 million a year scanning the sky for asteroids in Earth's neighborhood. They use Air Force telescopes in Hawaii, California and several other locations for their studies.
Because the objects are only easily seen as they get close to Earth, Morrison said astronomers will spot them as they cross the planet's orbit decades in advance of impact, or they will be discovered too late. "We would either have decades of warning, or we would see the flash of light in the sky and feel the Earth start to shake."
Copyright © 2002 FLORIDA TODAY
ASTEROID BIG ENOUGH TO RAZE FRANCE ZIPS BY EARTH
By The Associated Press
LOS ANGELES - An asteroid large enough to wipe out France hurtled past Earth at a distance of a half-million miles just days after scientists spotted it. The asteroid, dubbed 2001 YB5, came within 520,000 miles of Earth on Monday, approximately twice the distance of the moon.
Dozens of asteroids pass close by Earth each year, although 2001 YB5 was closer than most. On Friday, for instance, an asteroid known as 2001 UU92 will pass with 11 million miles of Earth.
Asteroid 2001 YB5, estimated to be 1,000 feet across, was traveling about 68,000 mph relative to the Earth when it zipped past. "It's a fairly substantial rock. If it had hit us at that sort of speed, you would be taking out a medium- size country, France, I suppose, or Texas, or something of that order," said Jay Tate, director of the Spaceguard Centre in Wales.
Astronomers with the National Aeronautics and Space Administration's Near-Earth Asteroid Tracking (NEAT) program discovered 2001 YB5 on Dec. 26. Soon after, astronomers calculated the asteroid's orbit and determined there was no danger it would strike Earth.
Had it been on a collision course, it would have created "one of the worst disasters in human history," said Steven Pravdo, the NEAT project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "What could we have done about it? The answer is not much," Pravdo said.
Copyright © 2002 The Seattle Times Company |
