By Mike Wall, Space.com Senior Writer | January 9, 2017
A smallish asteroid zoomed past Earth this morning (Jan. 9), just two days after scientists first spotted the space rock.
The asteroid, known as 2017 AG13, flew by our planet at just half the distance from Earth to the moon today at 7:47 a.m. EST (1247 GMT). (On average, the moon lies about 239,000 miles, or 385,000 kilometers, from Earth.)
2017 AG13 is thought to be between 36 and 111 feet (11 to 34 meters) wide, according to astronomers at the Minor Planet Center in Cambridge, Massachusetts. For perspective, the object that exploded over the Russian city of Chelyabinsk in February 2013, injuring more than 1,000 people, was thought to be about 65 feet (20 m) wide. [In Images: Potentially Dangerous Asteroids]
Initial observations of the object show that it takes about 347 Earth days to circle the sun, on an orbit much more elliptical than that of Earth
Surprise flybys like the one just performed by 2017 AG13 are far from unprecedented. Millions of asteroids are thought to cruise through space in Earth's neighborhood, and astronomers have detected just 15,000 of them to date.
The good news is that the vast majority of the behemoths — the ones capable of causing damage on a global scale if they were to hit Earth — have been discovered, and none of them poses a threat for the foreseeable future, NASA researchers have said.