Observing Perseid Meteors... Using a Radio
This August sees the return of the Perseid meteor shower and, with the moon setting around midnight on Aug 11, the early hours of the 12th should allow for a fantastic show. But say if you're clouded out?
The shower has been observed for around 2,000 years and the particles of dust making up the individual meteors we see today are likely around 1,000 years old. The meteor shower occurs when the Earth orbits through the dusty debris of comet Swift-Tuttle.
Whether the shower puts on a good show or not can often be irrelevant for us down here trying to watch. Cloud is an astronomer's archenemy but, like all villains, there are ways to defeat even the most dismal of weather conditions. I have a neat way you can 'watch' the Perseids even if you are clouded out.
The Perseid meteor shower gets its name from the place in the sky where the meteors all seem to originate -- in the case of the Perseids, they appear to come from a point in the constellation Perseus. I use the phrase 'seem' to come from because in reality there is a cloud of dust particles out in space that Earth passes through.
As we sweep up the particles of dust, they plummet through our atmosphere at speeds in excess of 60 kilometers per second, which makes our our fastest bullets, traveling at just over 1 kilometer per second, seem like tired snails! The energy associated with meteoric dust falling through our atmosphere causes the gas surrounding the meteor to glow, allowing us to see it as a streak of light across the sky.
The best time to observe meteor showers is in the early morning hours because you are on the 'forward facing' hemisphere of the Earth as it orbits the sun. It is a little like driving through a swarm of flies; the front of the car (Earth) will have lots of flies (meteors) squashed to the windscreen (forward facing hemisphere) but the rear will have none.
Meteor observing is definitely an early morning pursuit, but what can you do if it's cloudy? All is not lost.
As meteors whiz through the atmosphere, they ionize gas molecules creating a trail of ionized gas.
It is possible for radio signals to bounce off these ionization trails and these signals can be tuned in to, even when cloudy. The real beauty is that you can do it from the warmth and comfort of your car.
The trick is to tune your car radio to a commercial FM radio station that you cannot normally pick up, ideally one that is around 1000 kilometers away. You can find one by looking for big cities about that distance from you and then searching online for a suitable radio station transmitting from there.
Normally you will just hear a hiss of noise when tuned in from that distance, but as meteors zip in through the atmosphere, the distant radio waves will bounce off their trail, allowing you to hear the station for a brief moment. You might also hear pops and whistles as the meteors arrive.
Now sit back, turn the heated seats on, relax and listen to the sounds of the Universe as Earth gets pummeled by an ancient comet stream.