This illustration shows the path of asteroid 2012 DA14 as it swings past Earth on February 15. This side view shows that the asteroid will approach from below Earth's south pole, swing closest to Earth around mid-day, then depart above the north pole. The line that bisects Earth shows the path followed by satellites in geosynchronous orbit, 22,300 miles above Earth. The asteroid will pass between this ring of satellites and Earth, so it will not hit any of them. The asteroid will be too faint to see without a telescope. In the early evening of February 15, it will pass near the Little Dipper, low in the northern sky. [P.Chodas/NASA/JPL]
- Getting Close Keeping Track 
This giant radio dish at Goldstone, California, will track asteroid DA14 as it retreats from Earth February 16-20. The antenna is part of NASA's Deep Space Network, which communicates with spacecraft that are far from Earth, from the Messenger orbiter at Mercury to the Voyager probes at the edge of the solar system. The radio antenna, which spans 230 feet (70 meters), will act as a radar gun, emitting pulses of radio waves and tracking their echo off the asteroid, which is about 150 feet (45 meters) in diameter. Combined with other observations, that should reveal details about the asteroid's composition, mass, and rotation, as well as the subtle effects of solar radiation on its path around the Sun. The antenna couldn't track the asteroid on its in-bound path to Earth because DA14 was too far south. [NASA/JPL]
An asteroid the size of an office building will zip past Earth tomorrow afternoon. It’ll miss us by about 15,000 miles. That’s closer than any other asteroid will come this year — that we know of, anyway.
We don’t always know about such approaches too far in advance, though. This asteroid — designated 2012 DA14 — was discovered just a year ago, even though it’s passed quite close to us many times over the past century.
A telescope in southern Spain discovered DA14 as part of an automated search for asteroids that come close to Earth. Such asteroids could cause massive damage if they hit our planet, so it’s important to find them long before any potential impact.
Additional observations allowed astronomers to plot the asteroid’s orbit, which revealed the upcoming approach. The observations also showed that DA14 is probably around 150 feet in diameter. That’s not all that large, but at speeds of tens of thousands of miles an hour, an impact with Earth likely would cause extensive damage.
Several telescopes will track 2012 DA14 throughout its encounter with Earth and beyond. The observations will allow astronomers to plot a more precise orbit, letting us know how close the asteroid will come in the years ahead. The observations also will provide a more precise look at the asteroid’s size, shape, and composition — a scientific bonus from a very close encounter.
Script by Damond Benningfield, Copyright 2012
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