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The MAGIC telescopes caught a record-breaking gamma-ray burst from a black hole that lived 7 billion years ago.
Abstract
Astronomers detected a gamma-ray flare from a distant quasar — a cosmic beacon whose light traveled billions of years to reach us. It quickly faded, and the spectral cutoff at 50 GeV suggested the emission comes from fast particles colliding with radiation from the dusty "doughnut" around a black hole. How far can such rays reach?
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Seven billion years ago, a black hole at the center of a galaxy unleashed a gamma-ray flare — the most energetic form of light — with staggering power. Its light, after crossing cosmic distances, reached the MAGIC telescopes in December 2017. Along the way, the expansion of the Universe stretched the waves, making them longer. But the real surprise was yet to come: the radiation came not from the hole itself, but from the dust ring surrounding it.
The mechanism is like a game of billiards. Particles accelerated by the hole to nearly the speed of light slam into dust grains like target balls. This is how gamma-ray photons — packets of pure energy — are born.
By studying the spectrum (the breakdown of light by energy), astronomers confirmed that the dust acts as the target. A single such gamma-ray photon carries the energy of a mosquito bite, but packed into a volume smaller than an atomic nucleus. Flares like these are windows into the past: they show us how black holes function as particle accelerators when the Universe was half its current age.
🎯 A single gamma-ray photon from this quasar carries energy comparable to a mosquito bite — but concentrated into a volume smaller than an atomic nucleus. If such a photon hit a person, it would knock out a whole cascade of particles.
