A brilliant meteor seen over most of Western Australia about 7pm yesterday was unusual, but not unexpected, according to Guardian astronomy expert Dave Reneke. Mr Reneke said to expect an intense period of meteor activity over the next week or so, with the 'Orionids' meteor shower.

Comment: The Orionids are certainly on their way, though this 'meteor' was seen over most of Western Australia, which doesn't sound like just a part of the Orionids' meteor activity.

"The Orionids are one of the better showers of the year and are well known to produce 'fireballs,' slow-moving meteors that are actually on fire, producing a variety of colours and long, extended tails," he said. "It was more than likely the cause of the one spotted early last night.

"Once seen, these objects are seldom forgotten!" Mr Reneke said a meteor shower occurred when the Earth passed through the tail of a comet that came by years before. "When the Earth intercepts a debris stream, individual particles travel through the earth's atmosphere and start to burn up," he said.

"This time we are passing through the tail of Halley's Comet that came by in 1986.

"Meteors are typically seen around 100 km altitude, but the slower-moving ones, and the ones that are more spectacular - like the one last night - can actually appear to pass almost overhead.

"The Orionids can be seen in the early hours of the morning over the next seven days in the north-eastern skies between October 17 and 21."

He said the 'Orionids' were so named because they come from the direction of Orion the Hunter, a constellation better known in Australia as the Saucepan.