what was Monday's problem

An asteroid which may be as big as a ten-storey building has passed close by the Earth, astronomers say.

I do not know what you were up to on Monday or what worries you felt were important on that day but it could have been worse.

The object, known as 2009 DD45, thought to be 21-47m (68-152ft) across, raced by our planet at 1344 GMT on Monday.

The gap was just 72,000 km (44,750 miles); seems a lot but just think that this is only a fifth of the distance between our planet and the Moon.

It is in the same size range as a rock which exploded over Siberia in 1908 with the force of 1,000 atomic bombs.

The object was first reported on Saturday by the Siding Spring Survey, a near-Earth object search programme in Australia.

It was confirmed by the International Astronomical Union's Minor Planet Centre (MPC), which catalogues Solar System objects.

The closest recent flyby listed by the MPC is 2004 FU162, a small asteroid about 6m (20ft) across which came within about 6,500km (4,000 miles) of our planet in March 2004.

The latest object, 2009 DD45, passed by our planet at only twice the altitude of satellites in geosynchronous orbit.

In 1908, an object with a similar size exploded over Siberia, flattening 80 million trees over an area of 2,000 square km (800 square miles) near the Tunguska river.

"There is still a lot of debate over how big the Tunguska object was," Professor Alan Fitzsimmons, an astronomer at Queens University Belfast, told BBC News.

"It was always thought to be 50 or 70m across. But some recent calculations have implied it may have been even smaller than that - maybe down to 30m in size.