Supposedly, this new high-energy telescope is not a gigantic death beam cannon thing. Supposedly. What we're supposed to believe instead is that it's a brand new gamma-ray telescope, designed to search the sky for the likes of supermassive black holes, supernovae and pulsars.
Gamma rays are waaay out on the super high energy end of the electromagnetic spectrum. They're more powerful than X-rays, and while they can come from lots of places (including lightning strikes here on Earth), the most interesting ones are produced from exotic outer space phenomena like supermassive black holes, supernovae, pulsars, binary stars and other exciting things.
This new gamma ray telescope, called HESS II, is out in Namibia (just north of South Africa), where it has a good view of the southern sky. Its primary mirror is over 90 feet in diameter, comprised of 875 individually adjustable hexagonal micromirrors. Gamma ray telescopes are unlike other telescopes in that they don't actually look at stuff in space to see things in space. Instead, they're searching the upper atmosphere of Earth for what's called Cherenkov radiation.
You find Cherenkov radiation where you have particles moving through something like air or water at very, very high speed. It's what creates that blue glow in nuclear reactor cores, for example, when you get high-energy electrons moving through water. And if you have enough electrons, the Cherenkov radiation can be intense; better put on your lead underpants before watching this vid:*
Essentially, that blue flash is what the HESS telescope is looking for, except much, much fainter. HESS can detect the Cherenkov radiation flash from a single gamma ray interacting with our atmosphere 10 kilometers up, amounting to a release of just 100 photons per square meter over a few nanoseconds. By pinpointing the location of the flash and the direction that it came from, HESS can estimate where in the universe the gamma ray that caused it came from, gradually building up a map of very faint gamma ray sources.
See more of HESS in the gallery below, including an example of what the telescope actually sees.
*The dramatic flash here comes from "pulsing" the reactor. With a type of research reactor called a TRIGA reactor, it's possible to pull all of the control rods at once, causing the energy output to jump by a factor of 1,000 for 50 milliseconds. The reaction is self-regulating, meaning that it drops back down again to normal almost immediately, but the result is a huge power spike an a blinding flash of Cherenkov radiation.