Bert and Ernie are the nicknames IceCube researchers gave to two neutrinos, each carrying more than a quadrillion electron volts, that were recorded in 2012 and became the centerpiece of a result announced on November 21, 2013. They were part of a set of 28 events with energies between 30 and 1,200 trillion electron volts, collected between May 2010 and May 2012, that the IceCube collaboration said could not be explained by particles made in Earth’s atmosphere.
The detector behind the result is the one Francis Halzen conceived, and in 2026 it was the basis for his Nobel Prize in Physics.
Light sensors in a cubic kilometer of ice
IceCube instruments a cubic kilometer of clear Antarctic ice with 86 strings of sensors at depths between 1,450 and 2,450 meters. The 2013 release from the University of Wisconsin-Madison puts the total at 5,160 digital optical modules. A neutrino almost never interacts with matter, but now and then one collides with an atom in the ice and produces a charged particle that gives off a faint blue flash, Cherenkov light, which the modules record.
The facility is run by an international collaboration led by the Wisconsin IceCube Particle Astrophysics Center at UW-Madison and funded by the National Science Foundation, according to the university’s 2026 release. Interim Chancellor Eric Wilcots called IceCube “like no other telescope in the world” in that release, an idea to build a neutrino detector under almost a mile of ice that grew into a multinational, multi-institution collaboration.
Timing explains why the year attached to the discovery is a reporting year. The American Institute of Physics, in its note on the 2026 prize, says IceCube began full operations in 2011, and the analysis behind the 2013 result drew on data collected from May 2010 to May 2012 and, in Live Science’s account, a further analysis of that window turned up the 28 events after the first two were noticed in April 2012. The announcement came on November 21, 2013, and the paper followed in print a day later, so 2013 dates the report of the discovery and not the arrival of the particles.
Twenty-eight events against 10.6 expected
The collaboration’s paper, in the record held by the National Science Foundation, reports “28 neutrino candidate events (two previously reported), substantially more than the 10.6 expected from atmospheric backgrounds.” The excess deviated from standard assumptions for the atmospheric background at the 4 sigma level. Energies ranged from 30 to 1,200 TeV, and two events exceeded 1 PeV, the highest-energy neutrinos observed at that time.
Halzen, the principal investigator, chose the word “indication” rather than a stronger one. In the university’s release of November 2013 he called the data “the first indication of very high-energy neutrinos coming from outside” the solar system, and said it marked the dawn of a new age of astronomy. The results appeared in the November 22, 2013 issue of Science, with Olga Botner of Uppsala University as the collaboration’s spokesperson.
The qualifier in that claim is “high-energy,” and it carries weight, because neutrinos from beyond the solar system were not themselves new. The previous confirmed extraterrestrial neutrinos, as Live Science described them, came from a supernova in the Large Magellanic Cloud in 1987, and the IceCube events were, in Live Science’s phrase, more than a million times the energies of the 1987 ones.
Sci.News cites the paper as Science, volume 342, issue 6161.
Bert, Ernie and Big Bird
Spencer Klein of Lawrence Berkeley National Laboratory, quoted by Sci.News, noted that the 28 events included two of the highest-energy neutrinos ever reported, Bert and Ernie. A later analysis found a third, nicknamed Big Bird, with nearly double their energy. Sci.News reports that the leading candidate sources were active galactic nuclei, the particle jets from black holes consuming stars, though it says unknown accelerators might contribute too.
Uli Katz of the University of Erlangen-Nuremberg called the result “a major breakthrough” in Live Science’s report, and Nathan Whitehorn of UW-Madison described the evidence as really compelling that the neutrinos came from beyond Earth’s atmosphere and beyond the solar system. Live Science dates the two highest-energy events to April 2012, and gives the most energetic of all the 2010 to 2012 events as 1.14 PeV.
The university’s own timeline for the 2026 Nobel announcement lists the 2013 discovery as the first high-energy neutrinos from outside the solar system, and it notes that the result won Physics World’s Breakthrough of the Year Award. Later entries run from a 2017 detection of a neutrino from the direction of a supermassive black hole to 2022 and 2023 detections from active galaxies and from the Milky Way. IceCube’s own science page picks up the 2017 event, in which a multimessenger campaign following an IceCube alert gave the first evidence for a likely source of extragalactic neutrinos and high-energy cosmic rays: the distant blazar TXS 0506+056.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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