On 21st November, the IceCube Collaboration unveiled the first solid evidence of very high energy neutrinos originating outside of our solar system. This discovery represents a huge leap forward in the study of our universe. It is now possible to study the Universe not only due to electromagnetic radiation (e.g. visible light), but also because of neutrinos.
The details of this discovery are published in the world famous scientific journal "Science". Conducted by many, including researchers from the Université libre de Bruxelles (ULB) and the University of Mons (UMONS), this investigation has led to a scientific breakthrough which will allow for a better understanding of extreme phenomena, such as black holes, supernovae, pulsars and active galactic nuclei (AGN).
A technological and scientific wonder, IceCube is a neutrino observatory buried at the South Pole. Today, 25 years after coming up with the idea of using ice to reveal these elementary particles, the IceCube Collaboration has announced the observation of 28 extremely high energy events. For the first time, this discovery is evidence of the existence of astrophysical neutrinos produced in cosmic accelerators.
"This is the first sign of the existence of high energy neutrinos that originate outside of our solar system," said Francis Halzen, project coordinator in the United States and professor of physics at the University of Wisconsin – Madison. "It is a great joy to finally be able to broadcast this discovery after years of research. This undoubtedly marks the beginning of a new era in astronomy."
Neutrinos, subatomic particles of almost zero mass, rarely interact with ordinary matter and can thus provide us with unique information about the physics prevalent in the most distant and violent phenomena in the Universe. Every second, billions of neutrinos pass through every square centimetre of the Earth. The vast majority of these are still atmospheric and solar. Galactic and extragalactic astrophysical neutrinos are hence much rarer.
"The success of the IceCube experiment relies on the efforts of hundreds of people around the world," states Olga Botner, spokesperson of this collaboration and professor of physics at Uppsala University (Sweden). "This success could not have been achieved without the hard work of all the members of the IceCube Collaboration; from the design phase of the experiment and its implementation in a challenging environment – thereby proving the feasibility of the concept – to the gathering of data and subsequent analysis, all stages were conducted by members of our collaboration."
Published in "Science", this discovery reveals the first high-energy neutrinos to have ever been detected. This result is statistically significant (more than 4 sigma, in other words, a certainty of more than 99.99%) and is compatible with neutrinos of cosmic origin. The 28 events were found among the data collected by the sensor between May 2010 and May 2012 in an analysis to identify energy neutrinos above 50 TeV from any direction of the sky. These events cannot be explained by atmospheric sources or any other currently known high-energy mechanisms.
The IceCube observatory was designed primarily to detect high-energy neutrinos and identify their sources. The detector consists of 5160 optical modules deployed on strings buried 1500 to 2500 metres under the surface of the ice. These modules detect the Cherenkov light emitted from the charged particles which pass through the ice at high speed. The detector was finally completed in December 2010 after seven years of construction.
This project was created with the support of several agencies and programmes including the National Science Foundation in the United States, as well as the FRS-FNRS, the Belgian Science Policy Office (BELSPO) and the FWO in Belgium. This international collaboration currently involves more than 250 physicists and engineers from around the world (Australia, Belgium, Canada, Germany, Japan, New Zealand, South Korea, Sweden, Switzerland, USA and UK).
Four research teams from Belgian universities (Ghent University, Vrije Universiteit Brussel (VUB), ULB and UMONS) are currently working on the IceCube project and contributing to its success. These researchers are focusing primarily on scientific analysis as well as the operation and management of the daily detection systems, which should be operational over 99% of the time.
For more information, please consult: http://icecube.wisc.edu/gallery/press