There’s something wonderful about sitting under the night sky, watching a meteor shower play overhead. However, observers in the Southern Hemisphere usually find the shorter end of the stick, with most of the best showers being on the north side of the equator.
However, every May, southern observers get a special treat – the Eta Aquarid meteor shower. Conditions promise to be perfect this year, making it the ideal opportunity for some autumn meteor observations.
The forecast peak for this year’s Eta Aquariids falls on the morning of Saturday, May 7. [Australia-time, that is – if you’re in the US, see here – Ed.] The Moon is well out, so the meteor won’t get lost in its glare.
But what if the sky is cloudy? Well, if you missed the peak morning, don’t panic! The Eta Aquariids are renowned for their broad peak, and meteorite rates usually remain high for about a week (May 4–11) around the peak. So if it’s cloudy on Saturday morning, try looking again on Sunday or Monday as well.
To get the best view, you have to get up in the early hours of the morning and stay away from any bright lights of the city. Give your eyes time to adjust to the darkness. Take a chair or recliner to relax, unwind, and gaze up at the sky.
You won’t even need binoculars! To best view meteor showers, you’ll want to see as wide a sky area as possible. Using binoculars or binoculars will make the spectacle almost impossible to see.
Dust and debris from a famous comet
As the Earth orbits the Sun, it is constantly turned into dust and debris from comets and asteroids. Every April and May, Earth spends about six weeks crossing a river of dust left behind by the famous comet 1P/Halley.
Every 76 years or so, Comet Halley moves closer to the Sun. Its icy surface heats up until the ice boils into space in a process called “sublimation.” This pushes the comet into a gaseous coma, which is blown away from the Sun to form the tail of the comet.
The gas emanating from Halley’s surface carries the dust particles, which gradually spread throughout the comet’s orbit. Some are ahead of the comet, while others lag behind.
Over thousands of years, the space around Halley’s orbit has become thicker with dust particles. The comet is essentially moving beyond a nasty snow storm of its own making! And every year, Earth passes through that wide river of dust—giving rise to the Eta Aquarid meteor shower.
Interestingly, the Earth moves into Halley’s debris again in October, causing the famous Orionid meteor shower. But we get a better show every year in May with the Eta Aquarids, because that’s when we move closer to the center of the dust stream.
where should i look?
When the dust released by a comet hits Earth’s atmosphere, it forms a spectacular fiery streak of light in the sky. This usually occurs about 80 km (50 mi) above ground, although the largest pieces of debris can penetrate much deeper into the atmosphere before burning completely.
The dust grains in a meteor shower move around the Sun at essentially the same speed and in the same direction. This means that the grains are also traveling in the same direction as they hit the Earth.
But as they move toward an observer on the ground, their paths will diverge from that observer’s point of view, and they will appear to emerge from a point in the sky. That point is known as the “bright” of the shower.
The Orionid meteors show how the meteor shower appears to radiate from a single point. (Phil Hart)
Meteorites are named for the constellation in which their brightness lies. So the star in Eta Aquariides has a radiant near Eta Aquarii – the tenth brightest star in Aquarius.
To see the Eta Aquariids, you’ll have to wait until they’re radiant—before that, Earth’s body gets in the way. We’re lucky here in the Southern Hemisphere, because the Eta Aquarid Radiant rises in the east around 1:30 to 2 a.m. local time.
While the Eta Aquarid meteors can be seen anywhere in the sky, the ideal location to see the best numbers of meteors is about 45 degrees to the left or right of the radiant.
Luckily, this year we have another great view in the morning sky. The four planets – Saturn, Mars, Jupiter and Venus – will all be in a row. To see the best meteor show, look about 45 degrees to the left or right of this line of planets.
(Museum Victoria / Planetarium)
Above: Line of the planets and Eta Aquarid radiant as they will be visible from Sydney at around 4 p.m.
To see how the planets and brightness will rise from your location, visit the Stellarium Planetarium website, set your location, and advance the date and time to the morning of May 7. If you turn on “Constellation” and “Constellation Art” (at the bottom of the screen), you can watch Aquarius and the planets rise up from the comfort of your computer.
How many meteors should I expect to see?
The Eta Aquariids is the second best bath of the year for people in Australia. They can make a great show—but don’t expect meteors to fall like snowflakes.
When the radiant first rises above the horizon, at about 1:30, the meteors from the shower will be few and far between. If you see five or six eta aquarids in that first hour, you should probably consider yourself lucky.
That said, these early meteors may indeed be spectacular. Known as “Earth Grazers”, they often appear to streak across the sky from near a horizon. Meteors grazing on Earth are the result of meteors hitting our atmosphere at a very shallow angle, almost edge-on. They are rare, but incredible to witness!
As night falls, and the radiant rises higher in the sky, the number of meteors should increase. An hour before dawn, you could easily see 20 to 30 meteors per hour.
Oh, and a word of warning: meteors are like buses—if you’re anticipating 30 per hour, you can easily wait ten minutes and see nothing, before three come together. Go. Make sure you wear warm clothes so that you can stay under the stars for at least half an hour, if not more!
