House-sized asteroid whizzes past Earth
© ESA/P. Carril
An artist's depiction of a potentially hazardous near-Earth asteroid.
An asteroid the size of a house gave Earth a close shave today (April 18), passing nearer to our planet than any other space rock will for the rest of this year - that is, as far as we know.

Named 2019 GC6, the asteroid was discovered by NASA's Catalina Sky Survey near Tucson, Arizona, just last Tuesday (April 9), nine days before it flew by Earth. The giant rock made its closest approach this morning at 2:41 a.m. EDT (0641 GMT), when it whizzed by our plant at a safe distance of about 136,000 miles (219,000 kilometers), or slightly more than half the average distance between Earth and the moon.

At the time, the asteroid was traveling at a relative speed of about 12,600 mph (20,300 km/h), according to NASA's Jet Propulsion Laboratory. NASA estimated that the speeding space rock's diameter is "within a factor of two" of 49 feet (15 meters), which means it may be up to 98 feet (30 meters) wide.

NASA has classified 2019 GC6 as a "potentially hazardous" near-Earth object (NEO), but that doesn't mean that Earth was in danger when it flew by. The agency uses that term for any NEO that comes within 5 million miles (8 million km) of Earth's orbit and is massive enough "to cause significant damage on Earth," according to NASA's Planetary Defense Coordination Office.

Still, the fact that many asteroids go undetected until the last minute - or even after they have already made a close flyby of our planet - makes NASA's loose definition of a potentially hazardous object seem a little less reassuring. The closest asteroid flyby so far this year happened a day before astronomers first detected the asteroid, named 2019 FC1. That space rock, when it flew by on March 28, was less than half as far away from Earth as the asteroid 2019 GC6 was today, according to EarthSky.org.

To help keep Earth safe, NASA and other organizations around the world are constantly scanning the skies for new threats, cataloguing every space rock near Earth's orbit and studying new ways to stop an Earthbound asteroidbefore disaster strikes.

You can watch 2019 GC6's orbit animation here.