Part of being prepared is knowing what's out there. Trouble is, asteroids that may strike Earth, even big ones, can be hard to spot.
But you can spot them if you happen to have an infrared telescope in space. , an astronomer at NASA' in Pasadena, happens to have one of those at her disposal.
"Instead of seeing sunlight reflecting off their surfaces, we're actually seeing the heat that they give off," says Mainzer, who is also principal investigator for a spacecraft called (for Wild-field Infrared Survey Explorer). "We see them glow, essentially."
Even though space is a cold place, asteroids that come near Earth are warm. "They're orbiting the sun at roughly the same distance as the Earth," Mainzer says. "So they absorb sunlight, and the sunlight warms them up."
NASA had actually shut WISE off in 2011 when its main infrared detectors ran out of the coolant they needed to work properly. But WISE has other detectors that are good enough to spot nearby asteroids, so NASA decided to switch it back on. Now it's called Near Earth Object WISE, or .
Mainzer says the reawakened satellite started hunting for asteroids just before last Christmas. "Basically six days after we started taking survey data, we found our first new asteroid," she says. "And that was pretty exciting."
Right now, the job of keeping track of all the stuff that might hit Earth falls to the .
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