What are the Geminids?
The Geminids meteor shower occurs in mid-December each year and is one of the most reliable and most spectacular meteor showers visible from the southern hemisphere. The meteors are caused by small particles of rock and dust from the asteroid-comet (3200) Phaethon entering the Earth’s atmosphere. As they vaporise high overhead they leave long, bright and sometimes colourful trails across the sky. As Phaethon orbits the Sun it passes relatively close to the Sun, its surface bakes and crumbles in the sunlight and forms a surrounding cloud of dusty particles. These particles are larger than the typical dust from most comets which makes the Geminid meteors particularly bright and long-lasting. The meteors we see each December departed Phaethon long ago and formed a swarm of particles along Phaethon’s orbit. When Earth passes through this swarm each December, like a car driving through rain we see the Geminids meteor shower.
How can I see the Geminids?
For the best chance of seeing the Geminids plan ahead for this weekend, December 14-16, 2018. Early Saturday morning, from about midnight to 3am will be the best viewing time.
No telescope or binoculars are required. Your eyes are the best instruments for viewing a meteor shower.
Find a dark, country site with a clear view of as much of the sky as you can get – the whole sky if possible. If you are stuck in a city or a large town find the darkest (and safest) place you can – a large park, a coastal headland, a suburb on the outskirts. Take a blanket, something warm to wear and maybe something warm to drink – you will be awake for a while yet and it gets surprisingly cold lying still watching the sky.
Get yourself into position from about 11pm on Friday, get comfortable, lie back and watch the sky overhead and to the north. After 15-minutes your eyes will have adapted to the darkness. Now, every minute or two (more often if we are lucky) you should see a bright meteor fly silently overhead. Some will leave short trails, some will be faint. But, if everything goes to plan, some meteors will cross the whole sky from north to south, shining brightly and even showing a hint of colour! Once you see the first one you will be hooked for the night.
From a light-polluted city location only the brightest meteors will be visible. From a dark country site everything improves after the Moon sets at about 1am and the sky darkens. The show goes on until 3 or 4am. And you can stay as long as you like…
If Friday night is clouded out try again on Saturday night and maybe even Sunday night.
Unfortunately, Sydney Observatory is not open for this event. But your local observatory or astronomical society (see a list at http://www.quasarastronomy.com.au/australia.html ) may be holding an observing night.
Update [Dec 20, 2018]
While Sydney was clouded out (and stormed out!) over the weekend the Geminids were visible from other locations. They looked impressive from near Yass I heard and I saw a few bright, long meteors from the Blue Mountains…between the clouds. In 2019 the Moon will interfere at the best viewing time (early on Sunday December 15) but I will still be out there looking for the bright ones!