New window to the universe

Print edition : June 27, 2014

The IceCube Lab by night. It is a neutrino observatory whose dectectors are buried 1.5 km below the surface of the South Pole. Photo: Emanuel Jacobi/NSF

Figure 1: The cosmic neutrino spectrum: A low-energy background left over from the Big Bang is believed to suffuse the cosmos. Neutrinos have also been detected from the nearby explosion 1987A. Much of the spectrum of atmospheric neutrinos from cosmic-ray air showers has been measured by the Frejus underground detector (blue dots) near the South Pole. Not yet observed are neutrinos expected from cosmological point sources such as gamma-ray bursts and active galactic nuclei. The most energetic neutrinos are expected from the decay of pions created in collisions between cosmic-microwave-background photons and cosmic-ray protons with energies above 4x10(19) eV (the Greisen-Zatsepin-Kuz'min threshold).

Figure 2: This event display shows "Big Bird", the highest-energy neutrino at 2 PeV detected by the IceCube experiment. The colours show when the light arrived, with reds being the earliest, succeeded by yellows, greens and blues. The size of the circle indicates the number of photons observed. Photo: IceCube

With the recent discovery of very-high-energy cosmic neutrinos by the South Pole experiment IceCube, neutrino astronomy can be said to have finally arrived.

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