* Astronomy

600 Mysteries in the Night Sky

NASA's Fermi team recently released the second catalogue of gamma-ray sources detected by their satellite's Large Area Telescope (LAT). Of the 1873 sources found, nearly 600 are complete mysteries. No one knows what they are.
Gamma rays are by their very nature heralds of great energy and violence. They are a super-energetic form of light produced by sources such as black holes and massive exploding stars. Gamma-rays are so energetic that ordinary lenses and mirrors do not work. As a result, gamma-ray telescopes can't always get a sharp enough focus to determine exactly where the sources are.
For two thirds of the new catalogue's sources the Fermi scientists can, with at least reasonable certainty, locate a known gamma ray-producing object, such as a pulsar or blazar, in the vicinity the gamma-rays are coming from. But the remaining third - the "mystery sources" -- have the researchers stumped, at least for now. And they are the most tantalising.
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600 Mysteries in the Night Sky