May 2013

Paper is published announcing the discovery of two PeV-energy neutrinos, indicating an astrophysical neutrino flux

In May 2012, the IceCube group at Chiba University in Japan discovered two PeV-energy neutrinos in the data from the past year. One, nicknamed “Bert,” had been detected in the IceCube array in August 2011; the other, “Ernie,” had been captured in January 2012. While not statistically significant enough to claim a first observation of astrophysical neutrinos (2.8 sigma), the two events were a first indication of an astrophysical neutrino flux. The results were published on July 8, 2013, in Physical Review Letters. Read more here and here.

The two observed events from August 2011, aka Bert (left), and January 2012, aka Ernie (right)
The two observed events from August 2011, aka Bert (left), and January 2012, aka Ernie (right). Each sphere represents a DOM. Colors represent the arrival times of the photons, where red indicates early and blue late times. The size of the spheres is a measure for the recorded number of photoelectrons. Credit: IceCube Collaboration