Well, you might as well trash your copy of “Armageddon,” forfeit your dreams of pulling a Bruce Willis, and saving the world from an incoming asteroid: NASA on Thursday announced that there just aren’t that many space rocks out there that could threaten Earth, based on new findings from the agency’s Wide-field Infrared Survey Explorer (WISE).
The orbital infrared telescope recently completed the most accurate census of near-earth asteroids yet, determining that there are an estimated 20,500 mid-to-large size asteroids within a 120 million mile orbit of the Sun, not 36,000, as previously thought. That’s a 43 percent difference. Previous estimates were based on visible-light telescopes, which aren’t as accurate.
“The risk of a really large asteroid impacting the Earth before we could find and warn of it has been substantially reduced,” said Tim Spahr, the director of the Minor Planet Center at the Harvard Smithsonian Center for Astrophysics, in a NASA press release on the news.
NASA notes that the discovery fulfills the “Spaceguard” mandate issued by Congress in 1998, in which NASA was instructed to discover, track and catalog 90 percent of asteroids larger than 3,300 feet by 2008, even if it is three years behind schedule. The thinking was that “an object that size could devastate a small country and would probably destroy civilization,” as The New York Times wrote.
On Thursday, the agency reported that it had found and located 93 percent of these large objects, some 911 asteroids, leaving an estimated 70 that are still out there waiting to be located, according to the new WISE estimate.
Spaceguard was modified in 2005 to cover an even grander mandate: Finding and tracking 90 percent of near-earth objects with a diameter greater than 500 feet by 2020. NASA is still working on that one, noting that “mid-size asteroids… could destroy a metropolitan area if they were to impact in the wrong place…In addition, scientists estimate there are more than a million unknown smaller near-Earth asteroids that could cause damage if they were to impact Earth.”
NASA is publishing the new results in the Astrophysical Journal, but you can take a look at the revised charts on the NASA website and below.
As the agency explains, the WISE telescope achieved this feat by scanning “the entire celestial sky twice in infrared light between January 2010 and February 2011, continuously snapping pictures of everything from distant galaxies to near-Earth asteroids and comets.” That amounted to 11 pictures a second.
NASA also points out that the $320 million WISE telescope -launched in 2009 but temporarily decommissioned in February 2011 when its cooling and funding ran out – is the perfect tool for this job thanks to it’s infrared eye: “Asteroids of different sizes can look similar when viewed in visible-light. This is because visible-light from the sun reflects off the surface of the rocks… infrared detectors sense the heat of an object, which is more directly related to its size.”
