On Thursday night, an asteroid about the size of a 14-story building will hurtle past Earth at the mind-bending speed of 7 miles per second.
And one month ago, scientists didn't even know it existed.
Asteroid 2012 QG42 was just discovered on Aug. 26 by astronomers at the Catalina Sky Survey in Arizona.
It has been classified as a PHA (Potentially Hazardous Asteroid) by the Minor Planet Center based in Cambridge, Mass.
That sounds kind of scary, but scientists say there's no need to worry -- at least not yet. The asteroid is not expected to get closer to Earth than 7.5 x the distance of the moon from Earth.
(The moon's distance from Earth fluctuates, but it averages 230,600 miles).
Although the asteroid is estimated to be between 625 and 1,400 feet long, it will only be a magnitude 13 or 14 or about as faint as Pluto. That means you won't be able to see it with the naked eye, or even with a low-powered telescope.