IT COULD have put an end to our worries about the economy and those sharks at Sydney beaches.

At 12.40 yesterday morning, as the city slept, a previously unknown asteroid swept about 60,000 kilometres over the south-western Pacific.

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In astronomical terms it was a close call. Estimated to be between 30 metres and 50 metres wide, it passed almost seven times closer than the moon.

"No object of that size, or larger, has been observed to come closer to the Earth," said Rob McNaught, of the Siding Spring Observatory, near Coonabarabran.