STAND by for the celestial fireworks display of the year. From shortly after 11pm on Monday night, bright flashes of light will streak across the night sky as an avalanche of glowing meteors burns up in the atmosphere as shooting stars.
The annual sky show, known as the Geminid meteor shower, is expected, weather permitting, to be bigger and better than ever this year, thanks to a dark, nearly moonless sky.
"The waxing crescent moon will set early in the evening, providing people outside light-polluted areas with a relatively ideal view," said Swinburne University astrophysicist Dr Alan Duffy.
Although the meteors can come from any direction, most should originate from the north-east and will appear low on the horizon. "Ideally you don't want to have the [city] skyline or city lights in the way," he explained.
The shooting-stars show is best watched after midnight, peaking sometime between 2am and 4am on Tuesday morning.
"The meteor shower actually lasts for most of the night," Dr Duffy said. "But the sun rises at 5.52am and after 4am it begins to brighten enough to ruin it."
They are called the Geminid meteors because, if you trace them back along their path they seem to originate from somewhere near the Zodiac "twins" constellation of Gemini, representing Castor and Polydeuces, the twin sons of Zeus.
The space-rock Geminids are caused by the Earth ploughing through the dust grains and small pebbles in the debris tail from an asteroid named 3200 Phaethon.
"Phaethon's unusual orbit brings it to within less than half of Mercury's distance from the sun," said astronomer Dr Luke Davies from the University of Western Australia. "The sun's intense heat and gravity cracks the asteroid and causes it to leave a debris trail – and that's what we run into."
At this time of year, the Earth travels through the middle of the debris trail. "This year, the meteor count could be as high as 300 per hour," said John Rombi, former president of the Macarthur Astronomical Society of New South Wales.
Asteroids are remnants of the early solar system, forming out of the planetary disk around the young sun from which our retinue of planets formed 4.5 billion years ago.
"Unlike the Earth, asteroids have changed very little since they were formed and so give us insights into the material that was around in the early solar system," Dr Davies said.
This is what excites scientists about the Geminids. Being relatively slow-moving compared with other meteor showers – the Geminids travel at roughly 120,000 kilometres an hour against more than 300,000 kilometres an hour for the Leonid meteors – raises the chances of one or more space rocks making it all the way to the ground.
Scientists at NASA's Meteoroid Environment Office, which track the Geminids, are keeping their fingers crossed. "Finding an intact meteorite would be almost as good as analysing the results of a sample-return mission to Phaethon," Dr Duffy said.
This story originally appeared on www.smh.com.au
