The annual Leonid meteor showers promise to put on a spectacular show this year but Ireland looks set to miss the best of what is on offer. The showers will come in three peaks this year, the first at 10.01 a.m. next Sunday, November 18th, with two more peaks expected just before the sun sets. This should not prevent people staying out late or getting up early to watch for pre-dawn shooting stars, however. Leonid predictions can go awry and there will be a gradual build-up to the peak, explains David Moore, editor of Astronomy Ireland's astronomical magazine.
"The peak that is being predicted at 10.01 a.m. will have about 2,500 meteors per hour," he says. On a typical night, people might expect to see half a dozen or so.
"North America is the favourite for that peak. The west coast of Ireland is the most favoured in western Europe because that is where night will end last."
It gets even better, at least for those living along the western Pacific Ocean, he adds. A second peak is predicted to arrive at about 5.31 p.m. that Sunday afternoon Irish time, with perhaps 9,000 shooting stars per hour.
This will quickly be followed by another peak at 6.19 p.m. with up to 15,000 meteors per hour.
The last of the daylight could obscure the show for this island, but not where it is night anywhere in the northern hemisphere, from Central Europe across to the Pacific.
The hope among Irish enthusiasts is that the shower will build up gradually to the 10.01 a.m. peak, Moore says. "We are hoping that it will be spread out," with plenty of shooting stars to see in the hour or two before dawn.
The shooting stars seen during the Leonids come courtesy of a comet, P/Tempel-Tuttle, which passes through these parts once every 33 years. It is a cosmic litterbug, leaving dust and pebble-sized chunks behind in its wake. The Earth each November passes through this river of rubble, with the dust and rock burning up in the atmosphere 60km to 100km overhead.
The comet travels in a "retrograde" orbit, opposite to our own direction of motion. This means they strike the Earth's atmosphere at a colossal speed, 71km per second, increasing their brilliance and the numbers visible.
How good the shower will be and when it will arrive are now somewhat easier to predict thanks to work done by Dr David Asher of Armagh Observatory and Dr Robert McNaught of the Australian National Observatory.
Their studies help both to pinpoint when the showers will reach a peak but also how good they will be, and this year's display is expected to be vintage stuff, says Moore.
It all depends on where you are as the Earth enters the junk left behind by P/Tempel-Tuttle. Unfortunately for Ireland, it will be trapped in daylight when the peaks are reached. The island is ideally positioned for next year's show, however, with a peak of 15,000 meteors per hour expected to be reached by 4 a.m. on the morning of November 19th, 2002.
People should be ready to be surprised this year, Moore adds. If the peak on Sunday comes even a few hours early, then a great display might be on offer. It could still be good just before dawn if the shooting star rate builds up as expected.
No special viewing equipment is necessary and the best way to see the meteors is simply to get as far away from city lights as possible, sit back and just look up. The meteors will be visible as very short-lived streaks of light that can appear in any part of the sky.
Astronomy Ireland has initiated a "meteor watch" and asks the public North and South to count the numbers of shooting stars they see in any 15-minute period throughout the night and early morning of November 17-18th. Just start on the hour or any 15 minute interval and count the meteors seen. Times and counts can be sent to Astronomy Ireland, PO Box 2888, Dublin 1.