Year's first asteroid to hit Earth almost went unnoticed

A new asteroid has been identified before it hits Earth.

2014 AA is only the second incoming object astronomers have tracked this year before it hits our planet, and they almost missed it.

The first such object, 2008 TC3, was discovered on 6 October 2008 about 20 hours before it became a fireball over Sudan, New Scientist reported.

Astronomers were not so lucky with 2014 AA. Like 2008 TC3, the new asteroid was discovered with an automated telescope in the Catalina Mountains north of Tucson by the University of Arizona's Mount Lemmon Survey.

The survey automatically tracks moving objects and calculates preliminary orbits, and then posts the data to a network of astronomers for follow-up observations.

But 2014 AA's holiday-period arrival meant it nearly slipped by unnoticed.

The asteroid was 2 to 4 metres wide, which makes it a little smaller than 2008 TC3 and much smaller than the 17-metre-wide meteor that exploded over Chelyabinsk, Russia, in February 2013.

Objects of 2014 AA's size hit Earth every few months, and are too small to pose a threat to the planet.