The Eta Aquarid meteors appear to come from a spot near the faint star Eta Aquarii. Chart for 5 am AEST on 6 May 2014 as seen from Sydney. Chart Nick Lomb
On Tuesday and Wednesday mornings 6 & 7 May 2014 before dawn we have the opportunity to see one of the best southern hemisphere meteor showers, the Eta Aquariids. Fortunately, the Moon is at first quarter phase on Wednesday so that it is not brightening the sky on either morning.
To try to see the meteors find the darkest spot you can with no lights nearby shining in your eyes. For those in Sydney, you could try to avoid the city’s bright lights by choosing a viewing spot looking out over the ocean. Give yourself time to adapt to the dark for the meteors are generally fairly faint. They can appear anywhere in the sky, but it is probably best to face the north-east. That way the point from which the meteors appear to come, the radiant, is in your field of view. When you see a meteor you can trace it back to see if it did indeed originate from there.
As can be seen from the above chart, the meteors appear to originate near the star Eta Aquariid, that is, the star Eta of the constellation of Aquarius, and hence the shower is named after that star.
According to the International Meteor Organisation the peak of the shower is expected at about 5 pm on the Tuesday. At that time the radiant is below our horizon so the shower cannot be seen. However, the peak of the shower is reasonably broad so it is worth watching for the meteors on the Tuesday morning before the predicted maximum and on the Wednesday morning after the predicted maximum. From a dark spot with no clouds an Eta Aquariid meteor can be expected every few minutes.
The European Space Agency’s Giotto spacecraft imaged the nucleus of Halley’s Comet with dust being released from its dark icy surface in 1986. Copyright ESA. Courtesy of MPAe, Lindau
The origin of this meteor shower is Halley’s Comet as each year in early May the Earth runs into a stream of dust left behind by the comet. The comet itself is far away, almost at the furthest point of its long, elongated, oval-shaped path round the Sun. As the Earth moves into the stream small dust particles hit the Earth’s atmosphere at the fast speed of 66 km per second and burn up 100 km or so above our heads. This is what we see as meteors.
Halley’s Comet approaches the Sun every 76 years. Each time it does so it loses some of icy surface and with it a considerable amount of dusty particles. At the time of a close approach such as the last one in 1986, we see the ejected dust particles as the tail of the comet. Over the aeons that the comet has been circling the Sun these ejected particles have spread around its path around the Sun. We meet this dust stream each year in May when they give rise to the Eta Aquariids Meteor Shower and in October when the corresponding meteor shower is the Orionids.
Parallel railway lines appear to converge due to perspective. Courtesy Mark Hillary and Flicker
The particles in the stream hit the atmosphere in a parallel stream. It is the effect of perspective, as in the railway tracks pictured above, that the particles moving in parallel all appear to come from one point, the radiant.
Halley’s Comet will not be back in our part of the solar system until 2061. In the meantime, if you are willing to rise early on Tuesday and/or Wednesday morning, you can then have a go at catching sight of a few bits of this famous comet in advance!