This Summer’s Breakthrough in Multi-messenger Astronomy

For August 29, 2018    
Hi WN@TL Fans,
In January 1610 Galileo turned his 20x telescope towards Jupiter and discovered  moons in orbit around Jupiter—notably, the moons were not orbiting Earth.  That was a big deal, and a dagger in the intellectual gut of the geocentric system.
The discovery also is still a prime example of the power of looking skyward through new types of instruments that let us see beyond what is visible to the unaided eye.
Galileo’s telescope magnified light, something familiar to humans.  Since then, new generations of telescopes have seen not just by detecting visible light, but also by detecting other entities invisible to the eye, including radio waves, gamma rays, x-rays and even gravity waves.
Galileo published his discoveries in an essay entitled “Sidereus Nuncius” —
“Starry Messenger.”  Astronomers pay hommage to the metaphor when they use the phrase “multi-messenger astronomy” to describe the combined use of many types of waves, rays & particles to make a multi-layered map of the heavens.

This week (August 29Justin 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.

In 1609 Galileo had used his telescope to detect and map the mountains of the Moon.  By some accounts, he may have been expecting to see peaks on Jupiter.  In looking for mountains he found moons.  Sometimes, the most amazing discoveries are made while we’re looking for something else.
Next week (September 5)  Sarah Clayton of Anthropology will be here to take us back to the time of the Teotihuacan culture.  It’s not quite 4 billion years ago, but it’s a lot closer to home.
Hope to see you again soon at Wednesday Nite @ The Lab!
Tom Zinnen
Biotechnology Center & Cooperative Extension