Watching meteors in the night sky can be fun, although typically you only see a few flashes an hour. But there are certain times of the year when you can see many more — events known as meteor showers.
Picture: Tasayu Tasnaphun
These are caused by Earth moving through streams of debris left behind by passing comets and asteroids. Such showers are typically active for several days or even weeks, but usually feature short, sharp climaxes, or "maxima," with their best rates being visible on just a single night.
The coming year promises to be another good one for meteor buffs, so here's a guide on what to expect and how best to enjoy nature's own firework displays.
Alpha Centaurids: maximum February 8
The location of the Alpha Centaurid radiant at 4am on February 8, as seen from Perth.
Extending from January 28 to February 21, and peaking on February 8, this shower is known for producing brightly coloured fireballs with long-lasting trains varying from a few seconds to several minutes.
In most years, the Alpha Centaurids produce relatively low rates, with a typical maximum producing just six meteors per hour. But observers in 1974 and 1980 reported outbursts with rates of about 30 meteors per hour.
This year, unfortunately, the moon will greatly hamper observations. However, the International Meteor Organisation has predicted a possible outburst in activity, and have asked for observers to be on the lookout.
So despite the poor conditions, it could well be worth having a look — particularly given the frequency with which the shower produces bright fireballs.
Lyrids: maximum April 22
Radiant for the Lyrid meteor shower, as seen from Brisbane at 5am on April 22.
Observations of the Lyrids have been traced back through history for more than 2600 years — longer than any other meteor shower known. At the current epoch, however, they typically only yield moderate rates of perhaps ten meteors per hour, and are challenging to observe from Australia.
Despite this, the Lyrids are always worth a look, particularly if you have the good fortune to live far from light-polluted skies.
This year, there is the potential for them to put on a stronger-than-average display, and the moon will not interfere, making this an ideal opportunity to observe a shower with a long and storied history.
Eta Aquariids: maximum about May 6
The radiant of the Eta Aquariid meteor shower, as seen from Melbourne at 5am local time, on May 6.
Alert observers in the pre-dawn hours of early May each year are treated to a display of meteors whose parent comet, 1P/Halley (Halley's Comet), is the most famous of them all. Typically, the shower produces a few tens of meteors per hour — but in 2013, enhanced activity was observed, with rates as high as about 130 per hour.
In 2015, moonlight will greatly hinder observations at the time of the maximum — with the moon only two days past full. Nevertheless, the Eta Aquariids are one of the year's best southern showers, and still well worth observing, in the hours before dawn.
The Perseids: maximum about August 13
The radiant of the Perseid meteor shower, as seen from Darwin at 5am on August 13. The Perseids are only visible from the very northern reaches of Australia, just before dawn.
The Perseids are one of the year's most reliable and best showers — albeit one that is essentially invisible to Australian observers. For viewers in the northern hemisphere, however, they provide an annual summer treat that rivals the winter Geminids in intensity and spectacle.
The Perseids are fast, bright meteors, tied to the famous comet 109P/Swift-Tuttle, which is set to be particularly spectacular at its next perihelion passage, in 2126. The shower is active from mid-July to the end of August, but is at its best on the nights of the August 12 and 13, when rates often exceed 100 meteors per hour.
It will doubtless be possible to follow the shower online. And if you happen to be in the northern hemisphere at the time, the Perseids are well worth a look.
Orionids: maximum about October 21
The radiant of the Orionid meteors, at 1am local time in Melbourne on October 21.
The Earth again runs through debris left behind by comet 1P/Halley in October each year, causing the Orionid meteor shower. Though weaker than the Eta Aquariids, the Orionids are better known and better studied, as they are more favourable for northern hemisphere observers.
This year, the moon sets around midnight on the night of Orionid maximum, so those up after midnight could be treated to a display of perhaps a dozen fast-moving meteors per hour.
Taurid swarm encounter: early November
The radiant of the Taurid meteor streams, as seen at midnight local time in Melbourne, on November 5.
Through the course of the year, the Earth spends around five months ploughing through debris in the Taurid stream — thought to be a vast swathe of material left behind by the breakup of a super-comet, in the distant past.
Taurid meteors can be observed between September and December every year, with typically low rates throughout. The maximum usually falls in early November — when rates are usually of order ten per hour.
Every few years, however, the Taurids exhibit unusual behaviour. Somewhat elevated rates have been observed with each return of the "Taurid swarm". In addition, swarm returns seem to feature an increased number of bright meteors and fireballs.
Calculations suggest that there could be a strong return of the Taurid swarm this November, so it is well worth keeping watch during the early November, just in case!
The Geminids: maximum December 14 and 15
The radiant of the Geminid meteor shower, as seen from Brisbane at 11pm local time, on December 14.
The best shower of the year, the Geminids, is also the last of note for southern observers. This year, the maximum falls at around 3am or 4am on December 15, and conditions will be about as perfect as they can be for observation. The moon will be just past new, setting before the Geminid radiant — the point in the sky from where the meteors appear to originate — rises.
Once the radiant reaches a reasonable altitude (an hour or two after it rises), the Geminids will put on a spectacular display, with the best rates visible in the early hours.
At that time, the radiant will be at its highest in the sky, meaning we here in Australia have a prime seat to observe the maximum of the year's best, and potentially oddest, meteor shower.
Geminid meteors are relatively slow, and can often be both bright and long-burning — shining just a little longer than those from other showers. This is a direct result of their unusual genesis: they are the only meteor shower known to be parented by an asteroid, rather than a comet.
As a result, their meteoroids are denser and stronger than the norm. This means they can ablate — or shed material as they pass through the atmosphere — just that little bit longer before their flight is done, adding to the spectacle they produce.
The best way to see any meteor or meteor shower is to find a location well away from street lights. You can still watch for meteors from the middle of a city, but you will see reduced rates, thanks to the influence of light pollution.
Sit, or lie, under the stars for at least 15 or 20 minutes to let your eyes adapt to the darkness. Our eyes start to adjust immediately but it takes at least this long to fully adapt.
Remember, any bright light (such as checking your phone) will dazzle you. To avoid this, take a red light torch to help you find things — red light doesn't damage our dark adaption, so is safe to use when observing the night sky.
When observing, try to look about 30 to 45 degrees to the left or right of the radiant, and about 30 to 45 degrees above the horizon. This maximises the layer of atmosphere through which you'll be looking, while remaining high enough above the horizon that pollution and water in the air will not spoil the view.
If you want to report your sightings to help astronomers search for any possible meteorite falls, then check out the Fireballs in the Sky website and app, from researchers at Curtin University.
Jonti Horner is Vice Chancellor's Senior Research Fellow at University of Southern Queensland. Donna Burton is PhD Candidate at University of Southern Queensland. Tanya Hill is Honorary Fellow of the University of Melbourne and Senior Curator (Astronomy) at Museum Victoria.