Post by Verminda Spirit on May 6, 2006 7:20:54 GMT
Big new asteroid has slim chance of hitting Earth
18:21 02 May 2006
From New Scientist Print Edition. Subscribe and get 4 free issues.
David Chandler
Update 5 May 2006:
The newly discovered asteroid 2006 HZ51 has now been removed from NASA-JPL's list of potentially hazardous objects. The Earth is now safe from that particular threat, which was never anything more than a long-shot with odds of only one in six million. As explained in the original story (below), astronomers assumed that further observations would rule out any danger for the next century at least - and that is indeed what happened.
A newly discovered asteroid is now the biggest thing known with a possibility of hitting the Earth in this century – and it is also the one that could hit the soonest.
But the odds of impact currently stand at just one in six million, reducing the fear factor somewhat, and these odds should further diminish with additional observations. This latest addition to NASA-JPL's list of potentially hazardous asteroids was discovered on 27 April 2006.
The asteroid, called 2006 HZ51, has an estimated diameter of about 800 metres and is the one of the largest objects ever to make the list. An object of that size would cause widespread devastation if it did strike the Earth.
HZ51 also has one of the shortest lead-times to a potential impact of any such object yet found, and the shortest of any potential Earth-impactor currently on the list. The earliest of its 165 possible impact dates is just over two years away, on 21 June 2008.
Hollywood movies
Dan Durda, an asteroid expert and president of the B612 Foundation – which aims to anticipate and prevent such impacts – thinks the discovery of HZ51 highlights that at present there are no good options when faced with so little time to prepare. "There really isn't a whole lot we could do," he told New Scientist. "Most of the options that don't resemble a Hollywood movie involve deflection techniques that require many years or decades."
Other than stockpiling food and supplies and evacuating the regions most likely to be affected, he said, we would have to "hunker down and take the impact".
But this is an unusual case, statistically speaking. It is far more likely that Earth's nations would benefit from a much greater lead time before a potential impact, allowing more time for planning.
For example, the second-most imminent threat now on the list is the asteroid Apophis, which has about a 1-in-6000 chance of hitting Earth in 2036 – plenty of time to prevent it.
Altering orbits
The B612 Foundation has been pushing for a mission to place a tracking device on Apophis sometime in the next decade, so that the possibility of impact can be definitively proved or ruled out. The foundation also wants to send a mission to test ways of altering the orbit of a non-threatening asteroid, to test the viability of such methods.
But the chance of an impact by Apophis might be ruled out as early as this weekend, which will be the last chance until 2013 to observe it by radar, from the Arecibo radio telescope in Puerto Rico.
As for the newfound 2006 HZ51, the orbit calculations so far are based on just over 24 hours of observations, and so are likely to change quickly and should not be seen as a serious concern. As Clark Chapman of the Southwest Research Institute in Boulder, Colorado, US, explains: "Almost certainly, observations from one or two more nights will put this to bed as a zero probability."..
18:21 02 May 2006
From New Scientist Print Edition. Subscribe and get 4 free issues.
David Chandler
Update 5 May 2006:
The newly discovered asteroid 2006 HZ51 has now been removed from NASA-JPL's list of potentially hazardous objects. The Earth is now safe from that particular threat, which was never anything more than a long-shot with odds of only one in six million. As explained in the original story (below), astronomers assumed that further observations would rule out any danger for the next century at least - and that is indeed what happened.
A newly discovered asteroid is now the biggest thing known with a possibility of hitting the Earth in this century – and it is also the one that could hit the soonest.
But the odds of impact currently stand at just one in six million, reducing the fear factor somewhat, and these odds should further diminish with additional observations. This latest addition to NASA-JPL's list of potentially hazardous asteroids was discovered on 27 April 2006.
The asteroid, called 2006 HZ51, has an estimated diameter of about 800 metres and is the one of the largest objects ever to make the list. An object of that size would cause widespread devastation if it did strike the Earth.
HZ51 also has one of the shortest lead-times to a potential impact of any such object yet found, and the shortest of any potential Earth-impactor currently on the list. The earliest of its 165 possible impact dates is just over two years away, on 21 June 2008.
Hollywood movies
Dan Durda, an asteroid expert and president of the B612 Foundation – which aims to anticipate and prevent such impacts – thinks the discovery of HZ51 highlights that at present there are no good options when faced with so little time to prepare. "There really isn't a whole lot we could do," he told New Scientist. "Most of the options that don't resemble a Hollywood movie involve deflection techniques that require many years or decades."
Other than stockpiling food and supplies and evacuating the regions most likely to be affected, he said, we would have to "hunker down and take the impact".
But this is an unusual case, statistically speaking. It is far more likely that Earth's nations would benefit from a much greater lead time before a potential impact, allowing more time for planning.
For example, the second-most imminent threat now on the list is the asteroid Apophis, which has about a 1-in-6000 chance of hitting Earth in 2036 – plenty of time to prevent it.
Altering orbits
The B612 Foundation has been pushing for a mission to place a tracking device on Apophis sometime in the next decade, so that the possibility of impact can be definitively proved or ruled out. The foundation also wants to send a mission to test ways of altering the orbit of a non-threatening asteroid, to test the viability of such methods.
But the chance of an impact by Apophis might be ruled out as early as this weekend, which will be the last chance until 2013 to observe it by radar, from the Arecibo radio telescope in Puerto Rico.
As for the newfound 2006 HZ51, the orbit calculations so far are based on just over 24 hours of observations, and so are likely to change quickly and should not be seen as a serious concern. As Clark Chapman of the Southwest Research Institute in Boulder, Colorado, US, explains: "Almost certainly, observations from one or two more nights will put this to bed as a zero probability."..
