FM radio will pick up sounds from upcoming meteor shower
It’s one thing to see a meteor shower. But did you know that you can “hear” one, too? Just turn on the radio this coming Friday after-hours, and you will get to listen in on the approaching maelstrom of debris from Comet 209P/LINEAR as it plummets down through Earth’s atmosphere in the hours between Friday evening and early Saturday morning.
Meteors burn up as they enter Earth’s atmosphere, as they do, they emit gases. If the meteor is in the right altitude when these gases are seeping from it, then incoming radiation from the sun will ionize them. Once ionized, they will reflect traveling radio from distant locales and cause the waves to bounce to locations where they normally would not travel.
According to Joe Rao of Space.com, one zone in the atmosphere is critical to all of this: the ionosphere. This zone, which begins at around 53 miles above sea level and ends 370 miles above sea level, influences atmospheric electricity and human radio transmissions everywhere on Earth. The ionosphere reflects frequencies, but usually only those frequencies below 30 megahertz; frequencies such as those of the FM broadcast band pass straight through it.
The equation changes, however, when the sun’s radiation ionizes the ionosphere’s air particles. Then, even FM signals get bounced back down to Earth.
Rao calls particular attention to the ionosphere’s lowest zone, the “E layer,” which runs from 53 to 70 miles up. When the meteors pass through this layer, they may emit radio signals, too. And if they do, those signals will bounce down to ground level just like FM radio frequencies and be discernible on a personal FM radio.
The comets will first make their presence known to radio listeners in the form of brief bits of music or radio chatter cutting in from cities or towns very far off. If you hear those seemingly out-of-place transmissions breaking into the regular radio programming, you can be fairly sure that it began with meteors. You might also hear popping and whistling sounds, after which the transmission will fade away as the meteors’ ionization trail dissipates.
The trick will be knowing where to look. Rao advises tuning in to the lowermost-frequency end of the FM dial, below 91.1 MHz. A frequency where no nearby FM station is broadcasting will have the best chance of picking up some meteoric noise.
He also suggests tuning in to radio stations that are physically located to your east or west. This is because Comet 209P/Linear’s radiant will be toward the northern part of the sky. The stations will be even better meteor signal transmitters if they are between 800 and 1,300 miles from you.