Halleys Comet Meteor Shower
May 5, 2014

The Eta Aquarids Meteor Shower To Peak Overnight

John P. Millis, Ph.D. for redOrbit.com - Your Universe Online

As comets hurtle into the inner part of the solar system, the Sun’s radiation causes two tails to emerge. The first is primarily gas, vaporized by the heat of our star’s intense, warming rays. But while this glowing streak is what provides the visual imagery we normally associate with comets, it quickly fades as the comets moves across the solar system.

In contrast, the second tail is formed by the pressure of the solar wind as it literally tears the tiny dust particles from the comet's surface. And once created, it does not fade. Rather, the remnants of the tail leave a streak across the comets path – a trail of breadcrumbs telling the story of where the comet has been.

For comets that cross the orbital path of Earth, the dust left behind provides the source of one of nature’s most amazing sites – the meteor shower. When Earth reaches the remnants of the long departed comet, the tiny particles of dust are superheated in our atmosphere, causing streaks of light across our skies. They disappear nearly instantly as most of these microscopic chunks of rock are usually no more than the size of a grain of sand. It is rare that one would reach the ground. (Some objects – called meteorites – do reach the ground, but these objects are almost always associated with other events, and are rarely due to comets.)

And because the dust crosses our orbit at a fixed point, the resulting meteor shower is usually an annual event. Consequently, each major meteor shower is associated with a different comet, having passed through Earth’s orbit at some point in its history. Eventually, over the course of centuries, the dust will be consumed as the Earth takes its annual voyage around the Sun. But new events will arise, as new comets plummet towards the Sun, taking them across Earth’s path.

Viewing The Eta Aquarid Meteor Shower

Because of the annual nature of meteor showers, astronomers can predict, with great accuracy, when the events will reach their peak, and where on Earth will be ripe for the best viewing. The next major event is called the Eta Aquarid Meteor Shower – arising from material left behind by the infamous Halley’s Comet hundreds of years ago – and will reach its peak in the early morning hours of May 6, though events can generally be seen from late April to late May to a much lesser extent.

In general, major meteor showers are named for their radiant – the location in the sky where the meteors appear to emerge – usually associated with the closest constellation. In this case, the meteors will seem to materialize out of the constellation Aquarius, specifically near one of its closest stars: Eta Aquarii.

Generally, there are a couple of things to consider when evaluating how good the meteor shower will be. The first is the dust trail itself: how depleted has it become, and how many interactions are we likely to see? For the Eta Aquarid event, we can expect to see about one event every minute under optimal viewing conditions. This is pretty good, though other events later in the year will be better.

The phase of the Moon is also important. When the Moon is at or close to full phase, the sky's brightness can wash out the meteors, making them much more difficult to see. This year, we are lucky in that the Moon is only about one-quarter of its peak illumination.

However, there is a more significant problem for those of us in North America and Europe. At this time of year Aquarius doesn’t rise above the equator until about 3:00 am, and the morning twilight begins only about an hour later.

But even that hour is unlikely to produce many fireworks. Because it will be so low in the horizon, most of the meteors will be streaking away, below the horizon. Meaning that the event rate will be closer to 10 meteors per hour, or even less the farther north you are. And if you live in the northern part of the United States or in Canada, you’re unlikely to see any at all. However, those in the southern hemisphere can expect quite a show.

If you do happen to be up in the wee hours of the morning, it may still be worth a look as you may catch an Earthgrazer. These relatively rare events are characterized by their long-lived trek along the Earth’s horizon. They often leave colorful trails that can hang in the sky longer than normal “shooting stars”. Catching an Earthgrazer is certain to be a memorable event.