Space Watch IV 
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