The 2009 Perseid meteor shower. via
If you love the sight of fireballs streaking across the night sky, this is your week. The annual Perseid meteors are upon us, and not only is this the most spectacular meteor shower of the year, this one carries some weird baggage with it.
The Perseids are named for the constellation Perseus; from our Earthly vantage point this seems to be where the meteor shower originates. But it doesn’t. The Perseids appear every year around this time thanks to two reliable astronomical events: the Earth’s orbit around the sun and the Swift-Tuttle comet.
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The Swift-Tuttle comet was discovered independently by Lewis Swift and Horace Parnell Tuttle in July of 1862. It has an well-known orbital period of 133 years and a nucleus 26 miles across. And it leaves a trail of sand- and pea-sized rocky debris in its wake that’s grown over the years to stretch hundreds of millions of miles. Its last pass through our inner solar system was in 1992, and the comet itself won’t grace our skies again until 2126. Sorry you missed it.
It’s this debris trail that crosses the Earth’s orbital path. The Swift-Tuttle debris doesn’t come to us, we orbit into it, usually in mid-August. Since the rocky debris can’t dodge the Earth, some of the rocky particles, called meteoroids while they’re still in space, hit our planet’s atmosphere traveling at about 37 miles-per-second. They can’t survive entry into the atmosphere and instead ignite and burn, leaving a white-hot streak of superheated air behind them. That’s what we see.
The Perseids come from the constellation Perseus, which rises in the northeast after sunset. via
But don’t let our relatively recent (is cosmic terms, that is) discovery of the Swift-Tuttle comet fool you–the Perseids were around long before 1862.
Records of the Perseid shower go back nearly 2,000 years. In the year 36 AD, Chinese astronomers saw and recorded more than 100 meteors falling though the sky one morning. In 285 AD, the Perseid appeared around the torture and dead of Christian deacon St. Lawrence at the hands of the Romans. That this anniversary falls right in the midst of Perseid season has given the showers its sometimes nickname of the “tears of St. Lawrence.”
As an aside, legend has it that St. Lawrence was killed on a gridiron (imagine a flat grill) for spreading the Church’s wealth among the poor. While being grilled over a fire, he supposedly made one final quip to his prosecutors along the lines of “I’m done on this side. Turn me over!” Fittingly, St. Lawrence has become the patron saint of cooks and chefs.
It took a while for astronomers to understand that the Persied shower was an annual occurrence. It wasn’t until 1835 that Belgian astronomer Adolphe Quételet realized the meteors that fell every August were the same ones.
Another fun fact about the Perseids, and any meteor shower for that matter, is that you might be able to hear them. Science says sound doesn’t carry in a vacuum, so a rock falling and burning up in the Earth’s upper-atmosphere shouldn’t be able to make any sound that would carry far enough for us to hear. Rather, it’s the ionized trail that meteors leave behind them that you can hear. This trail reflects radio waves to produce an echo, and that radio wave transmits sound. You’ll need a radio, of course. Tune it to a quiet spot between stations, or better yet, find to a public or online radio station that will tune into the meteor shower for you.
The orbital path of the Swift-Tuttle comet. via
The Swift-Tuttle comet’s debris tail isn’t going anywhere just yet, so the shower remains a regular occurance. The Earth is going to keep passing through it every August.
The Perseids are the largest shower in term of meteors seen in a small amount of time; amateurs can see any where from 60 to 100 meteors falling through the sky every hours. This year’s shower is expected to peak very late Monday night and early Tuesday morning. So go outside sometime after midnight as far from city lights as you can manage. Lie flat on your back, let your eyes adjust to the dark for half an hour, and settle in for a while. It might take a couple of hours to see that high volume of meteors. A
As a bonus this year, the Moon is a crescent and will set before the meteor show really gets started, so you won’t have a giant light in the sky to contend with. Skywatching doesn’t get much better.
