Every year the Earth passes through a stream of cosmic debris that originates from a comet known as Swift-Tuttle. Named for its modern-era discoverers Lewis Swift and Horace Parnell Tuttle, who independently spotted it in July of 1862, this same comet was observed by Chinese astronomers as far back as the year 69 BC.
Like Earth, Swift-Tuttle is orbiting the sun, but its eccentric trajectory takes over 130 years to complete one full go-round. And all along the way, for at least the past couple thousand years now, this 16 mile wide cosmic snowball has been leaving bits and pieces of itself behind.
These bits and pieces, mostly microscopic in size, are accumulating in a gigantic elliptical dust cloud that extends throughout the comet’s orbital path. And, as it happens, the Earth’s own orbital path carries us right through that cloud of Swift-Tuttle residue from about mid-July through August.
So when we hit the densest spot around August 11-12, BINGO! That’s when we’re treated to a spectacular sky show known as the Perseid Meteor Shower.
(The Perseid's are so-named because these meteors appear to emanate from the direction of the constellation Perseus, which was itself named after an ancinet Greek dude who came long before Messrs. Swift and Tuttle, and even earlier than the ancient Chinese astronomers previously mentioned.)
Meteors, as most of you know, are the sudden flashes of light seen streaking across the sky when meteoroids (particles of matter from outer space) fall through the Earth’s atmosphere at such high velocities that heat from the overwhelming frictional forces creates a trail of glowing gas.
Well, they're either that, or they’re flaming arrows being fired at us from some disgruntled space monster, but either way, they’re pretty cool to watch.
And this year, 2016, the Perseid meteor shower is expected to be even more spectacular than usual with over 200 meteors per hour predicted to be visible to observers with clear dark skies.
Of course, if you don't have clear skies, which those of us in central Virginia never seem to have on August 11-12, you can probably expect to see approximately zero meteors. Nil, nada, zip, not even one.
But don't despair, The Multiverse Today has some alternative suggestions for observing this year's Perseid outburst:
1) Go somewhere else where the sky is dark and clear, and look up from about 1 am until just before dawn.
2) Try observing the meteors indirectly, by way of their effect on radio waves. That's where we can help . . .
It's a little known fact that falling meteors create trails of electrically charged regions in the ionosphere that are often capable of reflecting radio and television signals. This phenomenon was probably discovered by early amateur radio operators (Hams) who noticed their transmissions carried far beyond the normal range during periods of meteor activity. This "meteor scatter" effect has been well studied, and it's put to good use in situations where ordinary means of communication are either impractical or undesirable.
Radio meteor observing can become a fascinating and educational hobby, requiring only some simple, readily available, and inexpensive equipment to get started. In fact, one of the best methods for a beginner is to try listening for distant FM stations on a car radio.
Car radios tend to be more sensitive to weak signals than ordinary household receivers, and they're also more capable of tuning out stations on adjacent frequencies. Besides, once you're in a car you can drive to a nice remote site where there's not as much interference from your city's electrical noise.
The basic technique is to tune your radio to a frequency where there is no station coming in. Ideally, you should look for a frequency where there's also no signal, or only a very weak one, at each channel up and down from the primary one.
|Unfortunately, it's gotten pretty hard to find a completely vacant FM frequency these days, but it's not impossible if you're able to get away from congested areas. Then, while you're listening to "nothing" on the radio during a meteor shower, don't be too surprised if you suddenly hear something coming through from a station hundreds of miles away. It might last just a few seconds and may sound strangely distorted, but watch out - once you get the little thrill of knowing you just heard transmissions bouncing off a meteor you might get hooked.
Those of us in central VA, and in fact most of the northern tier of the U.S., also have the option of watching for meteor reflections from Canadian TV stations.
Oui, there are still a few dozen high powered analog TV stations operating in Canada, and they make ideal sources for monitoring meteor activity in the states. The catch is that you have to have an analog-capable TV set hooked up to a good old-fashioned roof top TV antenna.
So, if you are still analog TV equipped, try aiming your antenna to the North / Northwest and tune your set to one of the lower VHF channels. This technique works best with channels 2-6, while channels 2 and 5 have proven especially productive here at the Observatorium.