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Astronomers like Rik Hill scan the heavens from Arizona looking for errant asteroids. (Jason Millstein / iLLume Photography)

Asteroid Hunters

Astronomers are determined to protect human beings from inanimate outer space invaders

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Most of us do what we can for the environment, but Rik Hill’s actual job is to protect the planet. “Whoa, look at that!” he says, pointing at a moving blip of light on a computer screen. “It’s an unknown object. We just discovered one.”

We’re in an observatory on the summit of Mount Lemmon, a 9,000-foot peak north of Tucson, Arizona.

Hill’s boss, Ed Beshore, leans in and nods. “That’s an N-E-O,” he says, referring to a near Earth object. “It’s a nice one. It’s bright, and it’s moving fast.”

Hill, an astronomer, sends an e-mail to the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, where the Minor Planet Center monitors hundreds of thousands of small bodies in our solar system. The message gives the object’s coordinates at the time of its discovery so other astronomers can track it. And they’ll want to: an NEO is any asteroid or comet that will come within about 30 million miles of Earth’s orbit.

We’ll find out in the morning whether this NEO poses a threat. For now, Hill leans back, a cup of strong coffee in hand, and grins. “It’s not even midnight, and it’s a good night already,” he says. By dawn, he will spot two more.

I went to Mount Lemmon to see the top NEO hunters in action. Beshore and Hill are part of the Catalina Sky Survey, which has found about 2,500 NEOs in the past decade—including 577 in 2009, some 70 percent of the total discovered that year. The rocks range from the size of tables to mountains. Most will bypass Earth. But NEOs have plowed into our planet countless times before, and will do so again.

In October 2008, the survey’s Rich Kowalski observed a small NEO from this telescope. Within two hours, the Minor Planet Center used sightings by others to chart its trajectory. The asteroid would hit Earth in less than a day. Observers worldwide locked onto it, capturing 570 telescope images. NASA scientists calculated it would strike the Nubian Desert of northern Sudan. It was only the size of a small pickup truck, and most of it would burn up in the atmosphere. Even so, news of the imminent impact went all the way to the White House.

About 19 hours after Kowalski discovered it, asteroid 2008 TC3 lit up the sky above Sudan with the energy of more than 1,000 tons of TNT. Black fragments as large as apples landed in the desert. Two months later, NASA-led researchers collected hundreds of the extraterrestrial rocks.

In one sense, spotting the incoming asteroid was a triumph, because it demonstrated that astronomers can detect even a small projectile heading our way. But the feat was also sobering, because they saw it too late to do anything about it. Hill and his fellow NEO hunters hope to detect large asteroids sooner, preferably years or decades in advance.

“It’s the only natural disaster we can stave off,” says Don Yeomans, manager of NASA’s NEO command center at the Jet Propulsion Laboratory (JPL) in Pasadena, California.

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