In the early hours of Oct. 6, 2008, the astronomers who study objects in Earth's neighborhood in the solar system made a startling discovery: One of those objects was going to hit Earth. In 12 hours.
Alerts were sent out to asteroid hunters around the globe, and dozens of observatories turned their telescopes to spot the swiftly approaching threat. Researchers at NASA calculated the impact site — the Nubian Desert in northern Sudan — and dispatched a fleet of airplanes to watch it fall. Fragments scattered across the desert. A professor from the University of Khartoum brought his students to search for the pieces. The rocks turned out to be a rare type of meteorite called ureilite, and they showed that the meteorite contained amino acids — important molecules for life.
“They're something you can see in a telescope and also hold in your hand as a meteorite,” Nugent said. “So, in some sense, we get a free sample return mission on some of these guys.”
Asteroids are some of the oldest objects in the solar system — scientists call them the “building blocks of planets” — and they can tell us a lot about the origins of our world and the forces that have shaped it.
But that's not the only reason for hunting them. Nugent works at the space telescope NEOWISE, which uses infrared sensors to search for dark, nearby objects. The team has found more than 34,000 asteroids — including many near-Earth objects, whose closest approach takes them within 1.3 astronomical units of the sun. (An AU is the distance from the Earth to the sun, about 93 million miles.)
“Most astronomical work has to do with things that are very, very far away and don’t affect our lives very much,” Nugent said. “But asteroids, as you know, can come and hit Earth occasionally. So I think it’s important to find these objects so you can predict where they are going and potentially deflect one if we find one on the way to Earth.”
Speaking of Science gave Nugent a call to learn more about her book and life as an asteroid hunter. Our conversation has been edited for length and clarity.
Speaking of Science: How do you even hunt an asteroid? What's a day in your life like?
Carrie Nugent: The basic method to find asteroids hasn’t changed much in hundreds of years. So asteroids in a telescope look just like stars with one exception: They move with time. So to find an asteroid, you take an image of the sky, you wait a little bit, and you take another image of the same part of the sky, and you look for anything that moves between those images. That’s how the first asteroid was discovered. Obviously it wasn't with photographs; it was with drawings.
But these days we do the same thing. We have a telescope that takes images, and we use a very nice computer program to isolate the moving images. And then every potentially new asteroid is vetted by eye, so we take a look at each one, and then we send our observations to the Minor Planet Center.
SOS: Do you have a favorite asteroid?
CN: Not particularly. Back in the day, I’ve heard, particularly with the near-Earth asteroids, there were some asteroid hunters that knew the names of every one. But as of today on the minor planet website, there are 15,868 near-Earth objects discovered. So we’ve gotten past the time when we’ve memorized the names of each one. I like to think of them as an ensemble.
SOS: Why is it important to know where all the near-Earth objects are?
CN: I think most people are surprised to learn that an asteroid impact is one of the most predictable and preventable natural disasters. There’s been a lot of really great intensive research into earthquakes, but we can't predict an earthquake down to the day. We can’t predict where a hurricane is going to be a month in advance.
But the thing about asteroids is they’re physically very simple systems. So you can predict an asteroid's trajectory very precisely. If we can figure out where these things are going and know how to find them — and both those things we know how to do well — and you have the technology to deflect them, which we also do, then it’s really a solvable problem.
You want to find them now so you give yourself enough warning time so you can deflect them if you need to.
SOS: But asteroids have taken us by surprise before. Just look at 2008 TC3, the asteroid that landed in the Nubian Desert. Or the Chelyabinsk meteor, which exploded over Russia in February 2013.
CN: That’s certainly true. But it's useful to break down asteroids in terms of size. So we’ve discovered over 90 percent of asteroids 1 kilometer or larger across, and asteroid hunters are working toward a second goal, which is finding over 90 percent of the asteroids more than 140 meters across. 140 meters is pretty big, and the thing that exploded over Russia was only 20 meters. So what I really want to emphasize on finding the asteroids is, it's these really big ones. Certainly I wouldn’t mind finding the smaller ones, too, but, you know, you prioritize it based on size.
Another thing to keep in mind is that asteroids are all very different. Some asteroids are made out of metal, some are made out of rock, some are very loosely held-together accumulations of rock called rubble piles. Some rotate incredibly quickly in less than a minute, some rotate slowly. So your best option really would depend on the individual asteroid that you’re dealing with.
The best thing to do is to study these asteroids so we know the range of parameters we would have to deal with and also to find them so we have as much time as possible to prepare.
SOS: And if something big was headed straight at us, what would our options be? I'm guessing it wouldn't be like Bruce Willis in “Armageddon.”
CN: The thing I was surprised to learn is that sometimes the best thing to do is simply get out of the way. If it is a small enough asteroid and, depending on where it’s going, you might just want to evacuate the same way you would for a flood.
SOS: And if getting out of the way isn't an option …
CN: I was able to interview Lindley Johnson, who is NASA's planetary defense officer, which is the coolest job in the world, and he said there are three main ways being considered.
The first way is the gravity tractor, which is where you would put a spacecraft next to the asteroid and slowly try to tug it off its course. The other option is the kinetic impactor technique, where you would have something heavy hit the asteroid and give it a hard shove. And you know the one everyone thinks of as the nuclear option. The thing is, that might make for a great movie, but it’s not the most controllable and predictable of these methods. And because of that we call it a last resort. But the plan would be to explode a nuclear detonation nearby and then irradiate the surface, not to drill and implant a bomb.
SOS: You talk about all this very calmly. How worried should people be about a devastating asteroid impact?
CN: This is the only natural disaster we have the technology to prevent. The dinosaurs didn’t stand a chance, but we have telescopes and calculus and computers, and we can really do something about this. I like that aspect of it. This is something that could be solved in my lifetime. We could really chart near-Earth space and have all of these hazards mapped out and perhaps find there is nothing headed toward us, which would be really wonderful. Or perhaps it would give us the warning time we need.
By Carrie Nugent
Ted Books, Simon and Schuster. 108 pp. $16.99.
Correction: An earlier version of this post misstated the number of near-Earth objects NEOWISE has identified. The team has detected more than 34,000 asteroids, some of which are NEOs.