Aug 13 2009
listening to the Perseids meteor shower
The dust (sorry!) is starting to settle after 2 fantastic nights of participation in the annual Perseid meteor shower. The event hasn’t actually finished just yet but the number of meteors per hour will fall rapidly now that we have passed peak activity.
So what was it all about? I’m no astronomer, nor am I presumptuous enough to think I provide a decent explanation. Basically, our planet just passed through the debris trail left by a comet called Swift-Tuttle. You can find out more about the phenomenon here. What I have found astonishing is the sheer number of non-astronomers (myself included) who have been following events and staying up late to view these blazing trails of light as they stream across the night sky. How do I know that so many people have taken part? Well, that would be down to Twitter.
Many astronomers have seized the publicity available to them through the International Year of Astronomy 2009 to promote their work/research/hobby to people who have never had any dealing with astronomy before. The 365 Days of Astronomy podcast dedicated an entire episode to the Perseids just before they arrived. While these would have contributed to a raised awareness, they are not sufficiently mainstream to attract the unprecedented interest surrounding this year’s event – this is where Twitter comes in.
In the UK, a local astronomy group called Newbury Astronomical Society, who tweet from the @NewburyAS twitter account, seized the initiative by setting up the #meteorwatch hashtag for the Perseids event. The tag caught on and hundreds of people shared their experiences during the shower by tweeting with that hashtag, taking it to 4th place in Twitter’s trending topics. The organisation of the Newbury club even drew the attention of the BBC (click link on that page to see video footage) who visited “the bunker” during the first evening.
While the south of the UK enjoyed clear skies on the first evening, I was not so lucky. As there was no way I could see the meteors, I tried to detect them using a very basic radio technique instead. I connected an FM antenna to the back of an old Pioneer receiver unit and fed the output into a Griffin imic (with RCA to 3.5mm jack adapter) that was plugged into the usb port of a laptop. The Griffin components were essential to convert the RCA HiFi electrical connections into a standard computer connection.
I tuned the radio to the lowest clear FM frequency available (87.5MHz) and used a virtual chart recorder package call Radio SkyPipe to record the data. The recording software is quite straightforward and would be a good introduction to signals and measurement for senior pupils, such as those undertaking AH Physics investigations or the new Science Baccalaureate, as it requires several calibration & signal nulling steps before use.
Unfortunately I didn’t capture any exciting data although there was a curious low frequency amplitude modulation (see below) on the signal that I could not explain.
On the second night, I decided to leave the setting up of hardware for radio astronomy to the professionals and concentrated on looking for streamed data from the web. I found this site broadcasting from Tavistock in Devon. I downloaded the BS-Tuner application and pasted in the url of the broadcast site. To my surprise I heard streaming FM static coming from the laptop.
Every now and then this static was pierced by an eerie scream as radio waves were reflected back down towards the Tavistock antenna by the ionised wake of each meteor. The signals varied in volume, duration, clarity and complexity but due to their unpredictable nature it was difficult to record one. However I have attached one of the sounds I captured and encourage you to play it using the flash player below.
I was disappointed to view just a single Perseid at around 2.30am last night, the weather just wasn’t right for it. However, without those clouds I’d never have considered the potential for homemade radio astronomy.
A Nasa podcast on the Perseids is also available.
