Saturday, April 14, 2007

Don't trust TV

Well, you knew that right? I've just finished watching the first episode of Space, the documentary series hosted by Sam Neil for the BBC on video. I don't mind as such that an actor, not a scientist was hosting it (though I prefer people with degrees). What irked me was that the science advisors were either ignored or didn't vet the script.

The blunder? The idea that a star will become a supernova when it exhausts all of the hydrogen. But where - in the core of course. But wait, if a star is only ever hot enough to burn hydrogen then it won't go supernova. As hydrogen is consumed as helium in the core, it cools and collapses. There is a helium flash as the star begins to produce carbon. This heat initiates hydrogen burning in a shell around the core. This shell isn't as bound as tightly as the core, and so expands as it is heated and cools - hence a red giant. Stars have to get all the way to iron, which is the most stable element before rebounding into a supernova (I hope I've got that 100% right, it's been a while since I did astrophysics). The take home: be wary of dumbed down science on the small screen.

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