Australia is entering the peak viewing window for the Geminid meteor shower, with the annual celestial display forecast to reach its most active phase this weekend.
The shower occurs each December as Earth crosses a dense stream of debris left behind by an asteroid, triggering bright streaks of light as particles burn through the atmosphere.
This year's event arrives under near-ideal lunar conditions.
"The moon will be out of the way and the sky will be really dark — and that's why it's particularly good this year," Jonti Horner, professor of astrophysics at the University of Southern Queensland, said.
Astronomers rank the Geminids among the most reliable annual meteor showers.
What is the Geminid meteor shower?
The debris feeding the Geminids comes from the asteroid 3,200 Phaethon, which orbits the sun roughly every 1.4 years and has been shedding dust for hundreds of thousands of years.
That material now forms a two-week-wide ribbon of debris that Earth sweeps through annually, producing the surge in meteor activity.
"On Sunday night into Monday morning, we pass through the thickest part of the stream — that's when we get the strongest rates," Horner said.
Outside of major showers, he said most visible shooting stars come from much smaller, random debris.
"A typical shooting star is caused by something no bigger than a grain of sand burning up about 80 kilometres above the ground."
Where do the meteors appear from?
The Geminids take their name from the constellation Gemini, which contains the shower's radiant — the point in the sky from which the meteors appear to emerge.
Gemini sits near the bright stars Castor and Pollux and rises in the north-eastern sky during December evenings.
Although the meteors streak across the entire sky, Horner said they appear to trace back to a single point due to perspective.
"[It's the same effect] as if you look at a highway going into the distance and all the road lines appear to converge."
If Gemini is below the horizon, the display disappears.
"It effectively means the dust is hitting the other side of the Earth and we're facing the wrong way," he said.
When is the best time to watch?
The Geminid meteor shower runs until 24 December, but its most active period is expected between 14 and 15 December, when Earth passes through the densest part of the debris stream.
Across Australia, the Geminids' radiant rises between about 10pm and midnight, depending on location.
Visibility steadily improves as the night progresses, with peak activity expected between roughly 2am and 3am.
"The higher the radiant is in the sky ... the more meteors you'll see," Horner said.
Viewing is expected to remain strong through the pre-dawn hours before fading after sunrise.
Under ideal dark-sky conditions with no moon, international observers can sometimes see up to 120 Geminid meteors per hour near peak.
Where should you watch from?
While Australia doesn't offer the world's best vantage point for the Geminids — which favour the northern hemisphere — Horner said local conditions still allow for strong viewing.
"The further north you go, those are the best places in the world to see it ... but Australia still gets a very respectable show," he said.
"One of our big advantages is that people can easily escape light pollution."
He recommends observing from dark, open locations with clear horizons.
Designated Dark Sky locations such as the Warrumbungle National Park in NSW offer optimal conditions.
Organised viewing experiences, including guided night hikes, are also operating around the peak.
How can you maximise your chances?
Horner advises viewers to observe from midnight to 4am in non-daylight saving areas, or 1am to 5am where daylight saving applies.
He recommends lying flat or using a reclining chair to cover as much sky as possible.
"Find Orion (constellation) if you can and look about 40 degrees left or right. Pick an area that's quite good, dark sky," he said.
"Look about 45 degrees above the horizon and just lay back and relax."
Under clear, dark southern skies near peak, he said observers in southern Australia could see up to 30 meteors an hour.
"I always think meteors are like buses — you can wait 10 minutes and then three come along at once."
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