Eta Aquarids: Passing Through Comet Halley's Tail

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The Eta Aquarids can be a spectacular meteor shower. It peaks each year around early May and in the case of this year's shower, the peak is expected in the morning of May 6, but meteors from this shower can be seen between April 19 and May 28.

A few days ago, a fireball lit up the skies over Murmansk, Russia. It seems like Russia sees more meteors than the rest of the world. Why Russia? Trace and Discovery News Space Producer Ian O'Neill have the answer.
©iStockphoto/Antonis Papantoniou

We see the meteors when the Earth plows through the orbit of Halley’s Comet which means they are related to the Orionids shower in October, whose members are also the remnants of the same comet. The visibility of the shower tends to be a little better for observers around tropical and southern latitudes, but the Eta Aquarids can be seen further into the Northern Hemisphere and a good display can still be enjoyed.

It may seem a little strange that the shower is better from one part of the globe than the other but the reason is pretty easy to understand and it lies in the location of the radiant and the time of sunrise.

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The radiant is the point in the sky that all meteors from a given shower seem to appear and the constellation from which this point is centered is how the shower gets its name. In the case of the Eta Aquarids, the radiant lies very close to the star Eta Aquarii in the constellation of Aquarius.

At any given time, the radiant for the Eta Aquarids (or any other point in the sky for that matter) rises at the same local time for one location as it does for any other location. However, sunrise happens a little later in the southern hemisphere during May than it does in the northern hemisphere. This means that Aquarius has risen higher in the pre-dawn sky giving Southern Hemisphere observers a better chance of seeing meteors from this shower.

Observing Tips

Spotting meteors is a bit of a tricky business though and I have generally found that it is best to keep your gaze moving around, but focused on a point about 40 degrees away from the radiant.

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A really easy way to estimate 40 degrees is to stretch out your arm and, while keeping the palm of your hand facing away from you, stretch out your fingers. The distance from small finger to thumb is about 25 degrees so two of these will give you a rough estimate of 40 degrees.

Looking directly at the radiant means that any meteors appearing at that point in the sky will be heading straight for you and will burn up high in the atmosphere. However, as they will be heading toward you, any trail left by them will be very short and difficult to spot.

By far the best way to observe meteor showers is to get a few hours sleep before midnight then get up, wrap up warm and make yourself comfortable on a sun lounger or other comfortable seat, lie back and wait. You may be lucky and see one straight away but you may be there for some time so making yourself warm and comfortable is essential so you can stay the distance.

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You don't want to be cold and uncomfortable after half an hour and pack up only to find that others saw a wonderful display a few hours later. You do not need any other special equipment for meteor shower observing -- not even a telescope or binoculars -- so this is something anyone can enjoy.

If the weather is kind, then the astronomical forecast for this year's Eta Aquarids display is good. The moon will have set by the time the peak is upon us so the chances of seeing more meteors is higher.

Make sure your eyes are dark-adapted too as that can limit what you can see, but if you are lucky and patient then during the peak you might see as many as 50 in one hour. Good luck!

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