The observatory consists of photomultiplier tubes and thousand of spherical sensors located under the ice spread out over an area of greater than one cubic kilometer. The IceCube Neutrino Observatory is located in Antarctica at the Amundsen–Scott South Pole Station. Main article: IceCube Neutrino Observatory The Borexino experiment used this phenomenon to discover that the Sun releases the same amount of energy currently as it did a 100,000 years ago. Solar neutrinos leaving the Sun's core reach Earth before light does due to the fact solar neutrinos do not interact with any other particle or subatomic particle during their path, while light ( photons) bounces around from particle to particle. Solar neutrinos are able to provide direct insight into the core of the Sun because that is where the solar neutrinos originate. Photomultipliers are used as the detection device in this system as they are able to detect light for extremely weak signals. The detector is a complex structure consisting of photomultipliers, electrons, and calibration systems making it equipped to take proper measurements of the low energy solar neutrinos. The goal of the Borexino experiment is measuring low energy, typically below 1 MeV, solar neutrinos in real-time. Borexino is an actively used detector, and experiments are on-going at the site. The Borexino detector is located at the Laboratori Nazionali de Gran Sasso, Italy. ![]() This theory Pontecorvo had would make sense in accounting for the discrepancy between the experimental and theoretical results that persisted. In 1969, Bruno Pontecorvo, an Italo-Russian astrophysicist, suggested a new idea that maybe we do not quite understand neutrinos like we think we do, and that neutrinos could change in some way, meaning the neutrinos that are released by the sun changed form and were no longer neutrinos the way neutrinos were thought off by the time they reached Earth where the experiment was conducted. By the end of the 1970s, the widely expected result was the experimental data yielded about 39% of the calculated number of neutrinos. Davis even repeated his experiment changing the sensitivity and other factors to make sure nothing was overlooked, but he found nothing and the results still showed "missing" neutrinos. Many reviewed and redid Bahcall's calculations in the 1970s and 1980s, and although there was more data making the results more precise, the difference still remained. At the time, it was unknown if there was an error with the experiment or with the calculations, or if Bahcall and Davis did not account for all variables, but this discrepancy gave birth to what became known as the solar neutrino problem.ĭavis and Bahcall continued their work to understand where they may have gone wrong or what they were missing, along with other astrophysicists who also did their own research on the subject. To their surprise, the experimental value of the solar neutrinos present was less than 20% of the theoretical value Bahcall calculated. The entire experiment lasted several years as it was able to detect only a few chlorine to argon conversions each day, and the first results were not yielded by the team until 1968. By conducting the experiment deep underground, Bahcall and Davis were able to avoid cosmic ray interactions which could affect the process and results. The process was conducted very far underground, hence the decision to conduct the experiment in Homestake as the town was home to the Homestake Gold Mine. Davis developed the idea of taking hundreds of thousands of liters of perchloroethylene, a chemical compound made up of carbon and chlorine, and searching for neutrinos using a chlorine-argon detector. Once the theoretical value was determined, the astrophysicists began pursuing experimental confirmation. ![]() Using his model, Bahcall was able to calculate the number of neutrinos expected to arrive at Earth from the Sun. Bahcall, using a solar model he developed, came to the conclusion that the most effective way to study solar neutrinos would be via the chlorine-argon reaction. The experiment, known as the Homestake experiment, named after the town in which it was conducted (Homestake, South Dakota), aimed to count the solar neutrinos arriving at Earth. The timeline of solar neutrinos and their discovery dates back to the 1960s, beginning with the two astrophysicists John N.
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