On Oct. 12, 2017, the asteroid 2012 TC4 is slated to whiz by Earth dangerously close. The exact distance of its closest approach is uncertain, as well as its size. Based on observations in October 2012 when the space rock missed our planet, astronomers estimate that its size could vary from 12 to 40 meters. Beginning Wednesday, there will be a seven day window to track and estimate size, speed and direction more accurately.
That estimate translates to a distance of about 27,000 miles, which is about a eight of the way to the Moon. The chances of it hitting the earth are about one in 1 million.