(via APOD: 2012 July 27 - High Energy Stereoscopic System II)
H.E.S.S. II is one BAMF gamma-ray ‘scope.
Shown here in an “inactive” position, this big bad can move incredibly fast to detect the cherenkov radiation from gamma-ray bursts. The nice thing about having an atmosphere is that we don’t often get actually bombarded by gamma rays, which would be deadly (they’re what Marie Curie discovered). The not-nice thing is that, if you want to study gamma-rays, you need to be outside the atmosphere, generally. (That’s one of the things the Fermi Telescope is for.) However, gamma-rays aren’t stopped by much that exists out in the interstellar medium, so they travel a long way without losing much energy before they slam into the Earth’s atmosphere. The resulting collision produced a burst of high-energy particles in the sky that can be detected. This is detected as cherenkov light.
H.E.S.S. II is the second stage of the H.E.S.S. project, whose other, smaller members are a quartet placed around the bigger ‘scope. You can see one just behind the big one there.
This article about the ‘first light’ capture from H.E.S.S. II also has some links to the specs on this beauty. Among the issues with detecting gamma-ray bursts is that they don’t last very long, so once you’ve detected one, it’s important to get into position quickly. That can be tricky with a big telescope, but not for this one:
Gamma rays, as you might expect, come from some of the most cataclysmic events or powerful sources in the universe, so studying them is very important for a deeper understanding of cosmology.
Image Courtesy: H.E.S.S. Collaboration