June 2021 – Cosmic rays, neutrinos, photons, and gravitational waves: Each of these signals carries a message. What can they tell us?
For centuries, astronomers studying the stars were limited to information from visible light. Telescopes, photographic plates, and digital detectors were all developed to collect, magnify, and capture that signal.
But visible light isn’t the only message the cosmos is sending us.
“All the big, interesting events — like supernovae, gamma-ray bursts, and mergers — are disruptive,” says Péter Mészáros, a theoretical astrophysicist at Penn State. “They send out accelerated particles, photons, and waves in space-time.”
Astronomers call these messengers, and there are four types: photons, neutrinos, cosmic rays, and gravitational waves. Gradually, scientists have unlocked the ability to detect them all. Today, astronomers stand on the brink of a new era of multi-messenger astronomy — one they have been awaiting for decades and that is already providing new insights. Thanks to big instruments, big collaborations, and big data, they finally have the practical tools to interpret the cosmic detritus constantly raining down upon the Earth.