Extremely energetic charged particles called cosmic rays are accelerated by violent cosmic objects before raining down on Earth from all directions. Protons and heavier nuclei make up these cosmic rays, which can then collide with other particles in the atmosphere to produce secondary particles that cascade into so-called “air showers.” For more than a century, […]
Active galactic nuclei (AGNs) are leading candidates for the sources of high-energy astrophysical neutrinos—tiny, nearly massless particles—detected by the IceCube Neutrino Observatory at the South Pole. This is demonstrated by the real-time multimessenger detection of the blazar TXS 0506+056 and recent evidence of neutrino emission from NGC 1068 from a separate time-averaged study. However, the […]
When cosmic rays crash into the Earth’s atmosphere, air showers containing atmospheric muons and neutrinos are produced that rain down on Earth. During their journey, atmospheric neutrinos can morph or “oscillate” between three different flavors: electron, muon, and tau. These neutrinos can interact weakly with other particles and, thus, are still observable by detectors such […]
Neutrinos are tiny, nearly massless particles that traverse long distances across the universe, interacting with matter only through the weak force. They come in three different types, or “flavors”—electron, muon, and tau—and during their journey through the atmosphere and the Earth can transform, or “oscillate,” from one flavor to another. Over the last few decades, […]
Ever since high-energy astrophysical neutrinos were first observed in 2013, the IceCube Neutrino Observatory at the South Pole has been hunting for their astronomical sources. Active galactic nuclei (AGNs) are promising candidates as sources of astrophysical neutrinos given their very high levels of electromagnetic emission—from radio waves to gamma rays—that can outshine their host galaxies […]
Almost two years ago, the IceCube Neutrino Observatory at the South Pole announced evidence for high-energy neutrinos spewing from the “nearby” active galaxy NGC 1068. NGC 1068 is an active galactic nucleus (AGN) with a central, supermassive black hole that actively gobbles up surrounding matter. Classified as a Seyfert galaxy, NGC 1068 is not dominated […]
Neutrinos are tiny “ghostlike” particles that traverse long distances across the universe, interacting with matter only through the weak force. They come in three different types or “flavors”—electron, muon, and tau—and during their journey through the atmosphere and the Earth can transform from one flavor to another. This phenomenon, called neutrino oscillation, is a subject […]
As cosmic rays crash into the Earth’s atmosphere, air showers containing atmospheric muons and neutrinos are produced. The atmospheric neutrinos are then detected by DeepCore, a denser array of sensors in the center of the IceCube detector at the South Pole. Compared to the main IceCube detector, DeepCore is sensitive to neutrinos down to energies […]
The origins of extremely energetic particles, called cosmic rays, continue to puzzle astronomers. Some of the highest energy cosmic ray protons can reach one million billion electronvolts (PeV) in energy, but the sources of these protons, or PeVatrons, have been difficult to pin down. Cosmic rays accelerated by PeVatrons produce pions when interacting with surrounding […]
At the South Pole, the cubic-kilometer-sized IceCube Neutrino Observatory searches for high-energy neutrinos of astrophysical origin. When a neutrino crashes into the ice, blue light is emitted and detected by some of IceCube’s 5,160 digital optical modules (DOMs) across 86 vertical cables (strings) embedded deep within the Antarctic ice. The IceCube Upgrade, an enhancement to […]