A highrise-sized asteroid slipped quietly past the Earth yesterday, twice as close as the moon. We didn't see it coming.

Now designated 2017 AG13, the 10-storey (25-35m) tall space rock was spotted late Sunday by the Catalina Sky Survey. It was travelling at 16km a second.

"This is moving very quickly, very nearby to us," Eric Feldman, an astronomer with astronomy news website Slooh, said during a hastily arranged live broadcast of the fly-by yesterday.

He said the asteroid was roughly the same size as the one that exploded above Chelyabinsk, Russia, in 2013. That blast shattered windows and caused minor damage to buildings over a wide area. More than 1000 people were reportedly injured by flying glass and debris.


The orbit of 2017 AG13 will also take it through the path of Venus, he said.

It was roughly half the size designed to be detected by NeoCam, an infra-red telescope surveying the sky for potentially damaging asteroids that have orbits intersecting with Earth.

The programme last week received only partial funding from Nasa to continue its search.