A small rock in the Atlantic: The MAGIC telescope

This is the MAGIC telescope (Major Atmospheric Gamma-ray Imaging Cherenkov Telescope). It's perhaps the most exotic telescope at the observatory at the Roque de los Muchachos.

It's not an optical telescope. Instead of observing visible light, it's looking for gamma rays. Visible light is made up of different wavelengths, which give the different colours from red to violet. Wavelengths which are just a bit too short to see form ultra-violet (the stuff that gives you sunburn). Even shorter lengths are X-rays, and the shortest of all are gamma rays. The snag is that gamma rays don't get through the earth's atmosphere. But as they break up, they create a cascade of particles in the upper atmosphere, and the telescope is looking for these. By looking at the cone of atomic debris, the scientists can work backwards and find out which direction the gamma ray was coming from.

The nearer "basket" won't be operational until next year, but the father "basket" is already going strong. Instead of one big mirror, it has over 1,000 mirrors, each 50cm square, to form a compound mirror 17m (56 ft) across. That's the biggest telescope mirror in the world.

So where do gamma rays come from?

Some come from active galactic nuclei. These are the centres of distant galaxies, which are strangely bright. Astronomers believe this is because there's a super-massive black hole gobbling up the nearby stars. But they don't really understand the details, which is why they're keen to study them.

Supernova remnants are another source of gamma rays. When a large star runs out of its atomic fuel, it creates a massive explosion. Supernova remnants are the smoking gun, and the best available clue to understand supernovas. (Our own star is too small to explode in this way. Eventually it'll just fizzle out, but we have about four billion years before that happens.)

And the final source is gamma ray bursts. These are mysterious bursts of energy, which last anything from twenty seconds to two minutes. There's an orbiting satellite which watches out for them, and alerts the much larger, earth-based telescopes when it sees one. When that happens, MAGIC immediately turns to look at it. It's amazingly nimble for such a huge telescope. The whole basket weighs about 60 tons, but it can slew to point at any part of the sky within twenty seconds.

Arthur C. Clark once said that any sufficiently advanced technology was indistinguishable from magic. So you could say that MAGIC is magic.

Labels: astronomy, Canaries, Canary islands, La Palma, telescopes