A few hours from now (around 2 hours UT on April 9), a small ~20-meter in diameter asteroid will pass close to the Earth. At that time, asteroid 2010 GA6 will be about 10% closer to Earth than the Moon or 270,000 miles. Even though this is relatively close by asteroid standards, the small object will not be very bright (magnitude 15.5 to 16.0) and will be impossible to see without a camera-equipped telescope.
The asteroid was first picked up by the Tucson-based Catalina Sky Survey early on the evening of April 4. Events of this nature are detected a few times a year and may occur every few weeks. Still there is nothing to worry about. Space is big and these objects are small.
More info and a nice orbit diagram can be found at the JPL NEO Project Office.
The Transient Sky - Comets, Asteroids, Meteors 