December is here, which means the stunning Geminid meteor shower is primed to put on its spectacular annual show as it whizzes past the Earth. Unlike many of the year's biggest astronomical events, Australians are in prime position to get the best show from the Geminids this year. Here's how to watch it.
What Are They?
The Geminids are bits of debris from an object called 3200 Phaethon — a 'rock comet', or 'extinct comet' with an erratic orbit. This orbit brings it close enough to the sun that it passes within Mercury's orbit, resulting in the comet getting alternately baked and frozen and ultimately leaving a large amount of debris that the Earth passes through each year. It is this debris entering and burning up in the Earth's atmosphere that we see in the annual meteor shower.
The Geminids are distinct from other annual meteor showers due to the rarity of its parent object: while most meteor showers come from the debris of a normal comet, Phaethon is a rock comet, an object that shares similarities with both comets and asteroids. It also has an erratic orbit, meaning that every year the meteors are a bit closer to Earth and therefore a bit more visible.
If you're wondering where to look, the meteors are called Geminids because they radiate from the constellation of Gemini — or at least they appear to.
Watching The Show
This year, the Geminid meteor shower will reach its peak around midnight Friday December 14, AEDT. While the Geminid shower lasts for a couple of weeks, your best chance at seeing a good show is at the peak when it's at its most productive.
Thankfully the moon is cooperating this year — at the shower's peak it will only be in its first quarter, meaning there won't be too much light drowning out the meteors. However it'll still be best to watch it after midnight, once the moon has set.
Across the country, the Geminids will appear to the north, just above the horizon in the Gemini constellation. If you're not great with constellations or directions then a compass may be your best bet.
Where you are in Australia will also impact just how much you'll see. The further north you are, the higher up in the sky the radiant (the meteors' apparent point of origin) will be, and the easier time you'll have spotting them. For those in lower latitudes, look for a viewpoint up high with an unobstructed view to the north, ideally with no large cities spewing light pollution between you and the horizon.
Geminid Meteor Shower peak start times
So when should you tune in? The times that the radiant will begin to rise above the horizon is listed below for each capital city, although you won't be able to see much yet at that point. From that time onwards, however, the radiant will continue to rise above the horizon, providing a better view.
Brisbane around 9pm (AEST) Sydney: around 10:30pm (AEDT) Canberra: after 10:40pm (AEDT) Melbourne: just after 11pm (AEDT) Hobart: around 11:20pm (AEDT) Darwin: around 9:30pm (ACST) Adelaide: just before 11pm (ACDT) Perth: just before 10pm (AWST)
The timing is fairly forgiving whether you want to stay up late or get up early to watch the show. Make sure you don't rock up for a viewing at 5am, however, as first light is expected for around 5:10am in most places, and will spoil your view of the meteors.
Optimising Your Experience
Preparation is key: as well as setting your alarm for whatever time you've decided to go and see the Geminids, also prepare a chair and blanket so you can get comfy while you watch, and get out your camera equipment if you're planning on photographing the shower.
To get the best from this year's shower, remember the following tips for optimum meteor shower viewing:
- Reduce light pollution. The further away you are from any major cities, the better.
- Find a vantage point. The Geminids will rise higher through the night, but the higher up your viewing point is, the easier and earlier you'll see them.
- Use an app to locate the shower. Using a star viewing app can be the best way to locate the radiant point for the shower — in this case, the constellation Gemini. There are plenty of apps both free and paid for all platforms.
- Let your eyes adjust. The longer you sit in the dark, the more your eyes will pick up even when the meteors are very faint. Limit your phone use as much as possible, and turn on dark/night mode in advance if your phone supports it
- Scan the sky. While the Geminids emanate from a spot near the Gemini constellation, you may miss something if you only look in the one place. Remember to constantly be scanning for your best chance of seeing something.
If you're planning on photographing it, astrophotographer David Finlay recommends setting up with a tripod and cable release, and using the following settings for an optimal picture manual setting, 30 second exposure, f2.8 or lower (or as low as you can go), ISO1600-3200, white balance 4,200K. If you've got a big memory card, you can also lock the cable release button down and take a series of continuous photos. This way you're more likely to catch fleeting meteor trails, but you can also combine any photos into a great time lapse. To avoid a boring photo, he also suggests making sure something of interest is in the foreground so your photo isn't just plain sky.