Jason Shilling Kendall: Citizen Astronomer

William Paterson University
Amateur Astronomers Association of New York

Close Call with Asteroid 2012 DA14!


On Thursday, the Earth is in for a near miss. An asteroid half the size of a football field will pass by us with no danger to Earth. However, since it's passing very close to the Earth, we want to know more about this solar system neighbor. Asteroid 2012 DA14 might not have the flashiest or best name, but it's the "rock star" of the moment. It'll come within 17,000 miles of Earth on Friday, February 15 at about 3:00 pm Eastern Time. So, it's very tough to see from anywhere in the USA. In fact, by the time it's dark in the US, the asteroid will have moved away so far that only a large telescope will be able to see it. By large, I mean a telescope with at least a 12 or 15 inch diameter. That's not the kind of thing you can run out to the store and buy off the shelf. So, only people in Europe and Asia and Australia will be able to see it with a small telescope.

Are we in danger from it? In a word: no. It will pass close, about 17000 miles from the Earth, but that's far enough to call it a miss. And it doesn't have jets or an Evil Overlord that wants to shove it our way. In fact, lots of asteroids like these are out there, and they all miss the Earth all the time, because they never get this close.

What if it did hit? This rock, if it were to hit Earth, would create a big explosion and crater and would devastate a small city, if it hit one. If it landed on water, it would create a huge tsunami. But we do not have to worry about this at all. I'm glad that's not happening! I'd rather talk about good news!

Why did it come so close? Well, first, everything in the solar system orbits the Sun, going in the same way (counter-clockwise as seen from above), and the asteroids are no different. But not everything goes in circles. So, their paths cross. It's like watching a NASCAR race. They all go around the track, but they pass and dodge each other, and if the drivers didn't actively drive out of the way, the cars would hit each other. It's kind of hard to steer a planet, so things just gotta go the way they go, and sometimes they get really close.

The vast majority of all the asteroids live in the Asteroid Belt between Mars and Jupiter. It's like downtown Asteroidville. Jupiter, King of the Planets, occasionally bumps some of the asteroids from their happy home in the Asteroid Belt, and then they make a long trek around the Solar System. We know of about 40,000 asteroids in the belt, and can track about 3000 of them. They are staying out there quite happily. But there are a lot of Earth-Crossing asteroids that might one day hit Earth.

Are there other asteroids that pose a threat? Will we be hit soon? NASA's Near Earth Object program (NEO) is looking for them. In addition, there are lots of backyard astronomers who like hunting for them too. In fact, many asteroids are found by backyard astronomers. NASA then keeps track of them. The good thing is that space is REALLY BIG. The chance that any one asteroid to hit us is REALLY SMALL. Imagine going out to your high-school's football field and putting a single grain of sand somewhere on that football field. Now imagine going outside with a blindfold onto that field, walking out there, reaching down and picking up just that one grain of sand. That's the chance of an asteroid hitting Earth. But the Solar System is old, and there's a lot of asteroids, so eventually one will hit the Earth.

We keep track of asteroids not just to make sure they don't hit us, but also, one day we might want to mine them for resources like platinum and iridium. One big iron asteroid could make a lot of computer parts, and there are companies that are starting up today that will try to do just that in a decade or so. Also, we can study asteroids to learn more about the solar system's history. The Dawn Mission just finished orbiting the second largest asteroid Vesta, and is on to Ceres. We've learned a lot by looking up close for the first time at such an ancient world. In fact, all asteroids pretty much are like time capsules from the when the Sun and Earth and all the other planets are forming. If we could get samples, then we would know even more. (But we do, and they're called meteorites!)

William Paterson University Department of Physics American Astronomical Society Amateur Astronomers Association of New York Astronomical Society of the Pacific