Paola Gómez Padilla: Listening Meteor Showers

Meteor showers are something relatively “new” for science. Scientifics started studying them like 150 years ago. Before that, they were consider to be: “stars falling from the sky like rain” and “an atmospheric phenomenon”. Today, we know that meteors are a flash of light seen when a debris, or meteoroid, passes through our atmosphere. The meteors leave a trail formed by the flow of gases and the material they vaporize in their way. This trail is what make the “rain of stars” visible to us from planet Earth. However, this meteors can reflect radio way in the same way that the ionosphere is able to propagate transmissions between ham-radio operators. 

The ionosphere is known to reflect frequencies transparent to frequencies in the FM broadcast. This frequencies, which are short-wavelengths radio signals, can travel through the Earth’s atmosphere in straight lines. This means that a listener beyond the horizon will not be able to be reached by such frequencies. Nonetheless, the reflections can be signaled far away due to ionization of diverse layers in the upper atmosphere. This means that when a meteoroid vaporizes passing through the atmosphere, it can ionize air molecules in the path which can form expanding columns. The resulting ions are able to scatter and reflect radio waves, which generally last for few seconds due to rapid dispersion. At the lowest layer of the ionosphere, tiny particles vaporizes while larger particles flame higher up. Such meteors are known to reflect signals to farther transmitters due to the flame produced. 

On Earth, this meteor showers can be signaled by using a FM reception with no nearby broadcast, preferably lower than 91.1 MHz. Thanks to technological advances, with some materials easy to collect, in home or in a nearby store, like a stereo receiver radio and a computer program, we can do more than see a meteor shower. We can listen to it and also, record this beautiful event, even on daylight or cloudy nights, when we can’t see the meteors. This have a magnificent effect. The observation of a much known meteor shower, call Leonids. This was the latest meteor shower occurred, and we could listen to it, or to any other meteor shower.

We need a stereo receiver radio, an FM Yagi antenna, a computer, a male-male 1/4-inch audio cable, a program that can have a sound input and analyze the data, and speakers or headphones to listen to it. First, we have to turn on the radio to a frequency that don’t have any station at the moment (just static playing on the radio) while keeping the antenna horizontal orientation. Connect the audio cable into the headphones output of the radio, and into the microphone input of the computer. Open the program and start to record. When a meteor passes, its trail will reflect the radio waves, and it will produce an audible a peak on the wave shown at the program, making simultaneously a sound, like a note of a piano, but a little bit harsh. We have to adjust the receiver's volume until peaks of audio are under the maximum threshold of the radio strip chart. Two very useful programs for this experiment are Audacity and Radio-SkyPipe II.