The first-ever image of a black hole unveiled in 2019, shook the scientific community. The groundbreaking photograph from the Event Horizon Telescope (EHT) showed the supermassive black hole at the center of the galaxy M87. This iconic image, revealing the immense black hole known as Virgo A (NGC 4486), located in the constellation Virgo, was a landmark in astrophysics.
The same black hole is astonishing scientists again with a spectacular gamma-ray flare.
Gamma rays are the highest-energy form of electromagnetic radiation, billions of times more energetic than visible light. Such high-energy flares from black holes are exceedingly rare, and this particular one, lasting about three days, offers new insights into the extreme conditions near supermassive black holes.
It is seven orders of magnitude — tens of millions of times — more significant than the event horizon or surface of the black hole itself. The photons in M87’s gamma-ray flare have energy levels reaching a few teraelectronvolts. A teraelectronvolt is a way to measure the energy of tiny particles, and it’s roughly the same as the energy of a mosquito flying.
This is an enormous amount of energy for trillions of times smaller particles than a mosquito. These high-energy photons are much more powerful than those that make up the light we can see with our eyes.
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Weidong Jin, a postdoctoral researcher at UCLA and a corresponding paper author, said, “We still don’t fully understand how particles are accelerated near the black hole or within the jet. These particles are so energetic that they’re traveling near the speed of light, and we want to understand where and how they gain such energy. Our study presents the most comprehensive spectral data ever collected for this galaxy and modeling to shed light on these processes.”
VERITAS, a ground-based gamma-ray telescope located at the Fred Lawrence Whipple Observatory in southern Arizona, collected this data. More than 20 major observatories, both on the ground and in space, collaborated on this research.
These included NASA’s Fermi-LAT, the Hubble Space Telescope, and the NuSTAR, Chandra, and Swift telescopes, along with the world’s three largest imaging telescopes for detecting high-energy gamma rays (VERITAS, H.E.S.S., and MAGIC). These observatories are designed to detect X-ray photons and high- and very-high-energy gamma rays, enabling scientists to study the flare from multiple perspectives.
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A key part of this research involved analyzing the dataset called ‘spectral energy distribution,’ which describes how energy from astronomical sources, like M87, is distributed across different wavelengths of light. This analysis uncovered the different processes involved in the acceleration of high-energy particles in the jet of the supermassive black hole.
Further analysis revealed significant changes in the position and angle of the event horizon and the position of the jet. This finding suggests a physical connection between the particles near the event horizon and the jet. These changes in position may be influenced by different scales of size, meaning the behavior of the particles near the black hole’s event horizon could play a role in determining the position of the jet.
Jin said, “One of the most striking features of M87’s black hole is a bipolar jet extending thousands of light years from the core. This study provided a unique opportunity to investigate the origin of the very-high-energy gamma-ray emission during the flare and identify where the particles causing the flare are being accelerated. Our findings could help resolve a long-standing debate about the origins of cosmic rays detected on Earth.”
Journal Reference:
- J. C. Algaba et al. Broadband multi-wavelength properties of M87 during the 2018 EHT campaign, including a very high energy flaring episode. Astronomy & Astrophysics, 2024; 692: A140 DOI: 10.1051/0004-6361/202450497