This week (August 29) Justin Vandenbroucke shares the saga of this summer’s blockbuster discovery on multi-messenger astronomy: tracing a high-energy neutrino back to its source in a cosmic-ray-generating blazar at the heart of a galaxy far, far away.
Here’s how he describes his talk, entitled “Neutrinos from a Massive Black Hole Across the Universe”:
Four billion years ago, an energetic neutrino was emitted by a giant black hole at the center of a distant galaxy. After traveling across the universe for those four billion years, it collided with a molecule of ice in the middle of Antarctica on September 22, 2017. This produced a brilliant but fleeting flash of light, which was detected by the IceCube Neutrino Observatory led by UW–Madison at the South Pole.
In less than a minute, IceCube detected the flash, calculated the direction of the neutrino’s origin, and automatically alerted other observatories around the world.
Many telescopes then quickly pointed in the direction of the neutrino. In that direction was a massive black hole, known as a blazar, which was spewing out particles and radiation in two jets, one pointed right at Earth. At the time of the neutrino detection, the blazar was particularly bright in gamma rays, as measured by other telescopes including NASA’s Fermi Gamma-ray Space Telescope.
Analyzing previous data from IceCube, we also detected additional neutrinos from the same direction between 2014 and 2015. Although high-energy astrophysical neutrinos were discovered five years ago (also by IceCube), their origins have been a mystery and this is the first compelling evidence that we have identified one of their sources. This measurement is a milestone in neutrino astronomy, which is a key component of the quickly growing field of multi-messenger astronomy.
About the Speaker
Justin Vandenbroucke is an assistant professor at UW–Madison’s Wisconsin IceCube Particle Astrophysics Center. He is based primarily in the Physics Department, with a joint appointment in the Astronomy Department. Vandenbroucke received his PhD at UC Berkeley. He was then a Kavli Fellow at SLAC National Accelerator Laboratory and a NASA Einstein Fellow at Stanford University before moving to Madison in 2013.
In addition to his work on the IceCube Neutrino Observatory, Vandenbroucke leads construction of a camera for detecting the highest energy photons in the universe as part of the Cherenkov Telescope Array and is also the leader of the Distributed Electronic Cosmic-ray Observatory, a citizen science project which enables users to detect cosmic rays with their phones.
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