'Meteor fragment' could be space junk

An astronomy expert says that even if fragments of a spectacular meteor reached the ground in Canterbury, it is unlikely they will ever be found.

An unusual glazed black object was given to police by a farmer on Tuesday night after a blazing meteor shot through the skies over Canterbury, causing a sonic boom that shook buildings and frightened residents.

Yesterday the object was analysed by Christchurch's National Radiation Laboratory and considered unlikely to be from a meteor because it was only a tenth of the density expected.

The possibility of it being "space junk" could not be ruled out.

Canterbury University astronomy Professor Jack Baggaley said at some stage he would collect the object for further analysis by geology experts at the university. But he suspected it was simply an unusual-looking rock.

Mr Baggaley said if the meteor had been very solid and compact when it entered the Earth's atmosphere it was possible some pieces had reached the Earth. With information gathered from witnesses it was possible to estimate its trajectory, orbit and where fragments might have landed.

"But it is very difficult to identify [fragments]. Over farmland, it is an impossible task. Even if the area identified is within a kilometre, you might spend five years looking for it."

The National Radiation Laboratory was asked by the Department of the Prime Minister and Cabinet yesterday to analyse the object in case it was nuclear fuel from a spacecraft.

No radioactive material was detected, said laboratory general manager Jim Turnbull.

"We can state with some level of confidence it is not a meteor. It is possible it is some space junk or not related at all. Having said that, it is an interesting-looking thing and not obvious what it is," Mr Turnbull said. "It is probably not synthetic. Looking at its physical appearance it does look as though the material has been glazed and subject to high temperatures."

Meanwhile, a commercial airline pilot believes the event over Canterbury on Tuesday was space debris rather than a meteor.

The pilot said he was flying over Hanmer Springs at about 2000 metres when he saw spinning debris that reminded him of debris from the United States space shuttle Columbia when it exploded.

"First time I have ever seen anything like that during the day," he said.

He said the object was gone within seconds and it was impossible to judge how far away from the plane it had been, or the length of the object.