But it won't hit us, so you don't need to get all Deep Impact quite yet. NASA has promised us that much.
But still, the asteroid, poetically named 2005 YU55, is expected to come within 202,000 miles of Earth around 3:30 p.m. Pacific time today. Just so you know, 202,000 miles is closer than the distance of the moon from the Earth.
The asteroid is about a quarter of a mile wide, and you can see NASA's latest photo of the object here on this page. If you want to get a look, you'll need a good telescope and a sky chart, but even then it's going to be tough.
Here's what NASA's Jet Propulsion Labratory had to say about 2005 YU55.
At the point of closest approach, it will be no closer than 201,700 miles (324,600 kilometers) as measured from the center of Earth, or about 0.85 times the distance from the moon to Earth. The gravitational influence of the asteroid will have no detectable effect on Earth, including tides and tectonic plates. Although the asteroid is in an orbit that regularly brings it to the vicinity of Earth, Venus and Mars, the 2011 encounter with Earth is the closest it has come for at least the last 200 years.