Everything You Need to Know About Earth's Close Shave With an Asteroid

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On February 15, asteroid 2012 DA14 is scheduled to pay us a visit. The 150 foot (45 meter) rock has no chance of hitting us — but it'll be the closest approach that's ever been observed by astronomers.

Here's everything you need to know about this unique event.

Asteroid 2012 DA14 was discovered last year by astronomers in southern Spain using the La Sagra Sky Survey at the Astronomical Observatory of Mallorca. The object was about 2.7 million miles (4.3 million kilometers) away at the time. Subsequent analysis showed that it was heading right for us — and that it was going to give us a close shave.


A really close shave.

The asteroid, which is half the size of a football field and 130,000 metric tons in mass, will pass by our planet at a paltry distance of 17,200 miles (27,000 kilometers).


Putting that into perspective, the average distance from the Earth to the moon is 238,607 miles (384,000 km). That places the distance of 2012 DA14's closest approach to 1/14th our distance to the moon, or 7%. That means it'll pass to within about 3.5 Earth radii of the Earth's surface.

What's more, the asteroid's trajectory will put it closer to Earth than our satellites in geosynchronous orbit, which is about 22,245 miles (35,800 km) above the equator. That's about 5,000 miles (8,046 km) closer to Earth than those satellites.


Now, it's unlikely that 2012 DA14 will smash into a satellite, but NASA issued a warning to satellite operators anyway, providing them with detailed information about the flyby. But to reassure them, a NASA statement indicated that:

There is very little chance that asteroid 2012 DA14 will impact a satellite or spacecraft. Because the asteroid is approaching from below Earth, it will pass between the outer constellation of satellites located in geosynchronous orbit (22,245 miles/35,800 kilometers) and the large concentration of satellites orbiting much closer to Earth. (The International Space Station, for example, orbits at the close-in altitude of 240 miles/386 kilometers.). There are almost no satellites orbiting at the distance at which the asteroid will pass.


Nor will the asteroid hit the Earth — which would have been a Tunguska-like event were it to happen. "Its orbit about the sun can bring it no closer to the Earth's surface than 3.2 Earth radii on February 15, 2013," notes NASA.


At its closest point, 2012 DA14 will be above Sumatra, Indonesia at 2:24 PM EST (19:24 GMT).

This flyby represents a remarkable opportunity for astronomers to study a near-Earth object (NEO). To that end, NASA will be monitoring its approach using the Goldstone Solar Systems Radar in California's Mojave desert. One of the things that NASA will be interested in learning is how the flyby will impact on its subsequent trajectory shift. That said, the space agency is confident that it won't loop around for a return visit.


Astronomers are also curious to see what it looks like. They've already classified it as an S-type asteroid on account of its silicate composition, but it'll be interesting to see it from up close.

Regrettably, 2012 DA14 won't be visible with the naked eye. Its luminosity is estimated at a magnitude of less than seven, which is just beneath human visual capacity. Moreover, it will make its approach during daylight hours in the Western Hemisphere. That said, stargazers in the Eastern Hemisphere using a telescope — and with a bit of luck — might be able to catch a glimpse. The asteroid will look like a small pinprick of light zipping across the sky from the southern evening sky into the morning north sky.


And zip it will. Asteroid 2012 DA14 is moving extraordinarily fast, about 17,450 mph (28,100 kph). That's 4.8 miles per second (7.82 kilometers per second) relative to Earth.


Four minutes after its closest approach to Earth, the asteroid will pass into the Earth's shadow for about 18 minutes before reappearing from the eclipse. It will be within the Earth/Moon system for about 33 hours.

Scientists say there are about 500,000 near-Earth asteroids the size of 2012 DA14 in our solar system. Of those, less than one percent have been discovered. Flybys like this one only happen about once every 40 years or so.


NASA will be livestreaming this celestial event from the Marshall Space Flight Center in Huntsville. The action gets started at 6:00 PM EST on Friday February 15, and will run until 9:00 PM EST.

Sources: NASA (here and here), Space.com.

Images: Credit: ESA/La Sagra Sky Survey and NASA.