Another close flyby will be taking place on the night of February 23rd. I know it’s more than a week away, but I thought I’d get a head start on the doom-sayers. This time we’re being visited by a rock about the size of 1.5 to 3.5 football fields (160 – 350 m), which would survive its passage through the atmosphere and reach the ground as a fair sized meteorite. Lucky for us, it will pass some 3.5 million km (2.18 million miles) from Earth, which sounds very far away, but in astronomical distances is quite close as it’s only a little bit more than 9 times the distance from Earth to the Moon.
Diagram showing the orbit of asteroid 2011 CP4 in blue. Light blue is the part of the orbit that's above the plane of Earth's orbit while is dark blue is the part that's below. Note that the orbit of 2011 CP4 never crosses the Earth's orbit. The asteroid is shown at the point of its orbit when it's closest to Earth on February 23rd, 2012.
I’m providing a diagram of 2011 CP4′s orbit here (produced with JPL’s Small-Body Database Browser) so you can sleep at night without worry. Notice how the orbit of 2011 CP4 never crosses that of the Earth, which means it will never hit us. Unless it gets knocked off its path, but that’s unlikely! Again, sleep tight, the night won’t bite.