The three highest energy neutrinos, with energies of 1.0, 1.1 and 2.2 PeV, from left to right
Credit: IceCube Collaboration; NSF; University of Wisconsin

Bert, Ernie and Big Bird

The Universe is populated by nearly massless, electrically neutral particles called neutrinos. The existence of these particles was first suggested by Wolfgang Pauli in 1930 in a desperate attempt to explain some unusual properties observed in radioactive decay, but not confirmed experimentally until 1956. Neutrinos are produced by high energy atomic processes associated with the birth of the Universe, exploding stars, black hole eruptions, and perhaps, the annihilation of dark matter. Neutrinos rarely interact with matter (about 100 trillion neutrinos pass through you every second, without you noticing), and because of this, they serve as the most direct messengers of high-energy cosmic processes. But this same characteristic makes neutrinos extremely difficult to observe, requiring detectors of enormous size. A fascinating neutrino experiment called IceCube uses strings of detectors suspended in a cubic kilometer of the Antarctic ice sheet to detect the rare interactions of very high energy neutrinos with water molecules in the ice. The image above shows the detection by IceCube's strings of detectors of the three highest energy cosmic neutrinos yet observed. These three cosmic neutrinos, from left to right, are whimsically called Bert, Ernie, and Big Bird, after the well-known Sesame Street characters. No one is yet sure what produced these three neutrinos, but astronomers suspect powerful eruptions by supermassive black holes in blazars, a type of extremely active galaxy, as a a possible source. When will we find Elmo?
Published: May 23, 2016

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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 30-May-2016 10:02:03 EDT