'Jumped the gun'

But many astronomers did not agree that waking up President Bush would have been wise. "They completely misread the situation," said Benny Peiser of Liverpool John Moores University in the UK. "There was plenty of time to get other observers on the job." Others also believe the call would have been premature. "That would have jumped the gun before we knew much about the object," said Brian Marsden, of the Minor Planet Center.

Chapman was close to raising alarm

"I find it incredible that such action was contemplated on the basis of just four observations. That is just not enough to yield a sensible orbit.

"There was no need to panic as it was obvious that the situation would have been resolved, one way or another, in another hour or two," he told BBC News Online. Fortunately for all concerned, shortly after the ominous Chesley e-mail, an amateur astronomer managed to dodge the clouds and take a picture of a blank patch of sky. This was significant because if 2004 AS1 really was going to hit the Earth, it would have been in the amateur's sights. The fact that it was absent meant the rock would not strike us. But Chapman says in his presentation that if it had been cloudy, and no more observations could have been obtained at the time, he would have raised the alarm. Marsden disagrees. "If it had been cloudy and the call had been made to the President it would have been disastrous." Many astronomers recognise that they a false alarm could have brought ridicule on their profession. They are calling for more planning and less panic if it should happen for real next time. And 2004 AS1? It turned out to be bigger than anyone had thought - about 500m wide. It eventually passed the Earth at a distance of about 12 million km - 32 times the Earth-Moon distance, posing no danger to us whatsoever.

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