Extract from ABC News
In some parts of Australia more than 30 meteors will be seen per hour during the Geminid meteor shower. (Getty Images: bjdlzx)
Australia's best meteor shower is back this weekend, and this year will be a particularly good year to catch them.
The Geminid meteor shower will dazzle sky watchers with potentially dozens of meteors an hour as Earth moves through the debris of the asteroid known as 3200 Phaethon.
And there's a thin crescent Moon so the sky will be particularly dark when the highest number of meteors are visible.
According to Tanya Hill, an astronomer and curator at the Melbourne Planetarium, the December shower is not only spectacular because of its meteors, but also its origin.
"What's interesting about the Geminids is that it's left behind by an asteroid rather than a comet," Dr Hill says.
"That's a pretty rare occurrence."
When can I see the Geminids?
You will be able to see some meteors in the early hours of Saturday until Tuesday.
But the action really ramps up on Sunday 14 December and Monday 15 December as the shower peaks (see rates below).
To see them, you'll need to stay up after midnight on Saturday or Sunday night or get up very early.
"If you want the best chance, then you really want to look on Monday morning," Dr Hill says.
"Across the country, between 2 to 3:30am local time is when the peak will be."
How do I see the Geminids?
To see the Geminids, first you need to look towards the north-east, and try to find Jupiter.
The gas giant is one of the brightest objects in the night sky, and will be easily visible even in light-polluted areas.
Dr Hill says Jupiter will be close to Castor and Pollux — the two brightest stars in the Gemini constellation.
"Normally Castor and Pollux look really cool together … but Jupiter's going to make it little trio of stars."
The radiant point for the Geminid meteor shower will be visible in the north-east, and will rise around midnight in the eastern states. (ABC Science: Stellarium)
The Geminids gets its name because the meteors appear to "radiate" from the nearby Gemini constellation. This is known as a "radiant point", but meteors can streak across most of the sky.
Geminids meteors tend to be yellow in colour, as well as bright and fast.
Unlike last year, the Moon will be a small crescent so more meteors should be visible because the sky will be darker during the main meteor show.
How many meteors will I see an hour?
While the Geminids is the best meteor shower for the year, your location and the amount of light pollution in your area will influence how many meteors you'll see.
Below is an estimate for the number of meteors that might be visible in the early morning — around 2 or 3am — from each capital city around Australia under ideal conditions.
The further north you are, the better.
In northern parts of the country, in dark sky conditions, there may be more than 30 meteors visible per hour on Sunday morning.
In the south, it may be closer to 10–15 under dark sky conditions.
You will see less meteors per hour in areas where there is more light pollution.
While this may be lower than some reports from the Northern Hemisphere of up to 100 meteors per hour, the Geminids are still one of the best meteor showers for the Southern Hemisphere every year.
What's the best way to watch a meteor shower?
To make sure you get the most bang for your buck, Dr Hill says you need to take your time.
"You need to wait about 15 or 20 minutes for your eyes to get really dark-adapted," she says.
"That also means no looking at phones or any bright lights."
The Northern Hemisphere can see more meteors because the radiant point is higher in the sky than in the Southern Hemisphere. (Wikimedia: Dai Jianfeng, IAU OAE, CC BY 4.0)
Get cosy and comfortable, as Dr Hill notes that the longer you spend looking at the sky, the more likely you are to catch a few meteors.
"The other thing I always recommend is try to have someone share the experience with you, because that's what makes it more fun," she says.
"Especially if you're going to settle in for an hour or so, and then you can both be watching the sky and hopefully catch a lot of meteors."
What causes the Geminids?
While most yearly meteor showers are caused by the debris left behind by icy comets, the Geminid meteor shower is caused by an asteroid.
It's common for comets, which are balls of icy rock and dust, to drop a trail of dust and gas as they travel. But asteroids are large clumps of space rock, and normally don't leave much of a trail in their wake.
Asteroid 3200 Phaethon was discovered in the 1980s, and has a 1.4 year orbit around the Sun. This orbit is particularly odd, as it brings it extremely close to the Sun.
3200 Phaethon's orbit intersecting with Earth's orbit produces the Geminids meteor shower. (Wikimedia: Animation of 3200 Phaethon's orbit, Phoenix7777, CC BY-SA 4.0)
The asteroid has been referred to as a "rock comet", although it's not completely understood how 3200 Phaethon produces a debris trail.
Dr Hill suggests it may be to do with the heat of the Sun cracking the surface of the asteroid causing it to release dust.
"It's getting huge variations in temperature — from being really hot when it's close to the Sun and freezing cold when it's out beyond Mars," Dr Hill says.
"This has caused a whole lot of stress to the surface of the asteroid, which means that the rocks are breaking apart."
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