Paul Chodas and Don Yeomans, NASA/JPL Near-Earth Object Program Office
The small near-Earth asteroid 2012 DA14 will pass very close to the Earth on February 15, 2013, so close that it will pass inside the ring of geosynchronous weather and communications satellites. NASA’s NEO Program Office can accurately predict the asteroid’s path with the observations obtained, and it is therefore known that there is no chance that the asteroid might be on a collision course with the Earth. Nevertheless, the flyby will provide a unique opportunity for researchers to study a near-Earth object up close.
Asteroid 2012 DA14 will be closest to Earth on February 15, 2013 at about 19:24 GMT (2:24 p.m. EST or 11:24 a.m. PST), when it will be at a distance of about 27,700 kilometers (17,200 miles) above the Earth’s surface. This is so close that the asteroid will actually pass inside the ring of geosynchronous satellites, which is located about 35,800 kilometers (22,200 miles) above the equator, but still well above the vast majority of satellites, including the International Space Station. At its closest, the asteroid will be only about 1/13th of the distance to the Moon. The asteroid will fly by our planet quite rapidly, as a speed of of about 7.8 kilometers/second (17,400 miles/hour) in a south-to-north direction with respect to the Earth.
Even though 2012 DA14 is coming remarkably close, it will still only appear as a point of light in the biggest of optical telescopes because of its small size. Based on its brightness, astronomers estimate that it is only about 45 meters (150 feet) across. It will brighten only to magnitude 7.5, too faint to be seen with the naked eye but easily visible in a good set of binoculars or a small telescope. The best viewing location for the closest approach will be Indonesia, from which the asteroid will be seen to move at a rate of almost 1 degree per minute against the star background. Eastern Europe, Asia and Australia are also well situated to see the asteroid around its closest approach. But by the time the Earth rotates enough for observers in the continental United States to have a chance to see the asteroid, it will have receded and faded to about 11th magnitude. Radar astronomers plan to take images of the asteroid about 8 hours after closest approach using the Goldstone antenna.
2012 DA14 has not been in our catalogs for very long — it was discovered in February 2012 by astronomers at the La Sagra Sky Survey program in southern Spain and reported to the Minor Planet Center. The asteroid had just made a fairly distant passage by the Earth, about 7 times farther than the distance to the Moon when it was first detected by the Spanish group. Since 2012 DA14’s orbital period around the Sun has been about 368 days, which is very similar to the Earth’s, the asteroid made a series of annual close approaches, this year’s being the closest. But this encounter will shorten 2012 DA14’s orbital period to about 317 days, changing its orbital class from Apollo to Aten, and its future close approaches will follow a different pattern. The close approach this year is the closest the asteroid will come for at least 3 decades.
This passage of 2012 DA14 by the Earth is a record close approach for a known object of this size. A few other known asteroids have flown by the Earth even closer, but those asteroids were smaller. On average, we expect an object of this size to get this close to the Earth about once every 40 years. An actual Earth collision by an object of this size would be expected much less frequently, about once every 1200 years on average.
