The jet emerging from M87’s supermassive black hole is tens of millions of times larger than its event horizon.
- In 2019, the Event Horizon Telescope captured the first-ever image of a black hole at the center of the galaxy M87, located in the Virgo constellation.
- An international team of researchers, including scientists from UCLA, recently observed a teraelectronvolt gamma-ray flare from this black hole.
- The flare was seven orders of magnitude — tens of millions of times — larger than the black hole’s event horizon.
- Such a powerful outburst, not seen in over a decade, provides valuable insights into how particles like electrons and positrons are accelerated in the extreme environments near black holes.
Black Hole Imaging
The world was captivated in 2019 when the Event Horizon Telescope (EHT) released the first-ever image of a black hole — the supermassive black hole at the center of the galaxy M87, also known as Virgo A or NGC 4486, located in the constellation Virgo. Now, this cosmic giant is surprising scientists again with an intense gamma-ray flare, emitting photons billions of times more energetic than visible light. Such a powerful outburst hasn’t been seen in over a decade, providing valuable clues about how particles like electrons and positrons accelerate near black holes’ extreme environments.
Discovery of a High-Energy Flare
The jet coming out of the center of M87 is seven orders of magnitude — tens of millions of times — larger than the event horizon, or surface of the black hole itself. The bright burst of high-energy emission was well above the energies typically detected by radio telescopes from the black hole region. The flare lasted about three days and probably emerged from a region less than three light-days in size, or a little under 15 billion miles.
Understanding Gamma Rays
A gamma ray is a packet of electromagnetic energy, also known as a photon. Gamma rays have the most energy of any wavelength in the electromagnetic spectrum and are produced by the hottest and most energetic environments in the universe, such as regions around black holes. The photons in M87’s gamma-ray flare have energy levels up to a few teraelectronvolts. Teraelectronvolts are used to measure the energy in subatomic particles and are equivalent to the energy of a mosquito in motion. This is a huge amount of energy for particles that are many trillion times smaller than a mosquito. Photons with several teraelectronvolts of energy are vastly more energetic than the photons that make up visible light.
Accretion and Jet Dynamics
As matter falls toward a black hole, it forms an accretion disk where particles are accelerated due to the loss of gravitational potential energy. Some are even redirected away from the black hole’s poles as a powerful outflow, called “jets,” driven by intense magnetic fields. This process is irregular, which often causes a rapid energy outburst called a “flare.” However, gamma rays cannot penetrate Earth’s atmosphere. Nearly 70 years ago, physicists discovered that gamma rays can be detected from the ground by observing the secondary radiation generated when they strike the atmosphere.
Research Methods and Observations
“We still don’t fully understand how particles are accelerated near the black hole or within the jet,” said Weidong Jin, a postdoctoral researcher at UCLA and a corresponding author of a paper describing the findings published by an international team of authors in Astronomy & Astrophysics. “These particles are so energetic, 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, along with modeling to shed light on these processes.”
Jin contributed to the analysis of the highest energy part of the dataset, called the very-high-energy gamma rays, which was collected by VERITAS — a ground-based gamma-ray instrument operating at the Fred Lawrence Whipple Observatory in southern Arizona. UCLA played a major role in the construction of VERITAS — short for Very Energetic Radiation Imaging Telescope Array System — participating in the development of the electronics to read out the telescope sensors and in the development of computer software to analyze the telescope data and to simulate the telescope performance. This analysis helped detect the flare, as indicated by large luminosity changes that are a significant departure from the baseline variability.
Collaborative Observations and Data Analysis
More than two dozen high-profile ground- and space-based observational facilities, including NASA’s Fermi-LAT, Hubble Space Telescope, NuSTAR, Chandra and Swift telescopes, together with the world’s three largest imaging atmospheric Cherenkov telescope arrays (VERITAS, H.E.S.S. and MAGIC) joined this second EHT and multi-wavelength campaign in 2018. These observatories are sensitive to X-ray photons as well as high-energy and very-high-energy gamma-rays, respectively.
Insights into Particle Acceleration and Cosmic Rays
One of the key datasets used in this study is called spectral energy distribution.
“The spectrum describes how energy from astronomical sources, like M87, is distributed across different wavelengths of light,” Jin said. “It’s like breaking the light into a rainbow and measuring how much energy is present in each color. This analysis helps us uncover the different processes that drive the acceleration of high-energy particles in the jet of the supermassive black hole.”
Further analysis by the paper’s authors found a significant variation in the position and angle of the ring, also called the event horizon, and the jet position. This suggests a physical relationship between the particles and the event horizon, at different size scales, influences the jet’s position.
“One of the most striking features of M87’s black hole is a bipolar jet extending thousands of light years from the core,” Jin said. “This study provided a unique opportunity to investigate the origin of the very-high-energy gamma-ray emission during the flare, and to identify the location 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.”
Reference: “Broadband multi-wavelength properties of M87 during the 2018 EHT campaign including a very high energy flaring episode” by J. C. Algaba, M. Baloković, S. Chandra, W.-Y. Cheong, Y.-Z. Cui, F. D’Ammando, A. D. Falcone, N. M. Ford, M. Giroletti, C. Goddi, M. A. Gurwell, K. Hada, D. Haggard, S. Jorstad, A. Kaur, T. Kawashima, S. Kerby, J.-Y. Kim, M. Kino, E. V. Kravchenko, S.-S. Lee, R.-S. Lu, S. Markoff, J. Michail, J. Neilsen, M. A. Nowak, G. Principe, V. Ramakrishnan, B. Ripperda, M. Sasada, S. S. Savchenko, C. Sheridan, K. Akiyama, A. Alberdi, W. Alef, R. Anantua, K. Asada, R. Azulay, U. Bach, A.-K. Baczko, D. Ball, B. Bandyopadhyay, J. Barrett, M. Bauböck, B. A. Benson, D. Bintley, L. lackburn, R. Blundell, K. L. Bouman, G. C. Bower, H. Boyce, M. Bremer, R. Brissenden, S. Britzen, A. E. Broderick, D. Broguiere, T. Bronzwaer, S. Bustamante, J. E. Carlstrom, A. Chael, C.-k. Chan, D. O. Chang, K. Chatterjee, S. Chatterjee, M.-T. Chen, Y. Chen, X. Cheng, I. Cho, P. Christian, N. S. Conroy, J. E. Conway, T. M. Crawford, G. B. Crew, A. Cruz-Osorio, R. Dahale, J. Davelaar, M. De Laurentis, R. Deane, J. Dempsey, G. Desvignes, J. Dexter, V. Dhruv, I. K. Dihingia, S. S. Doeleman, S. A. Dzib, R. P. Eatough, R. Emami, H. Falcke, J. Farah, V. L. Fish, E. Fomalont, H. A. Ford, M. Foschi, R. Fraga-Encinas, W. T. Freeman, P. Friberg, C. M. Fromm, A. Fuentes, P. Galison, C. F. Gammie, R. García, O. Gentaz, B. Georgiev, R. Gold, A. I. Gómez-Ruiz, J. L. Gómez, M. Gu, R. Hesper, D. Heumann, L. C. Ho, P. Ho, M. Honma, C.-W. L. Huang, L. Huang, D. H. Hughes, S. Ikeda, C. M. V. Impellizzeri, M. Inoue, S. Issaoun, D. J. James, B. T. Jannuzi, M. Janssen, B. Jeter, W. Jiang, A. Jiménez-Rosales, M. D. Johnson, A. C. Jones, A. V. Joshi, T. Jung, R. Karuppusamy, G. K. Keating, M. Kettenis, D.-J. Kim, J. Kim, J. Kim, …, D. A. Williams, S. L. Wong, Z. Chen, L. Cui, T. Hirota, B. Li, G. Li, Q. Liu, X. Liu, Z. Liu, J. Ma, K. Niinuma, H. Ro, N. Sakai, S. Sawada-Satoh, K. Wajima, J. Wang, N. Wang, B. Xia, H. Yan, Y. Yonekura, H. Zhang, R. Zhao and W. Zhong, 13 December 2024, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202450497
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5 Comments
It says in the above article that “gamma rays cannot penetrate the Earths’ atmosphere.” This is untrue, because I have seen it stated in other reports on this site that nearby “gamma ray bursters” may have been responsible for some previous mass extinctions. So, would someone please inform me of the truth of this?
It is a matter of scale and significance. The article describes how cosmic gamma rays weren’t discovered until instruments had been lifted above the troposphere. (High altitude balloons reach 20 – 40 km, while the weather carrying troposphere is about 20 km high.) So for most purposes it is the atmosphere that shields us from the remaining 10 % of cosmic rays – mostly charged particles – that the vast heliosphere magnetic field doesn’t shield out.
Gamma ray bursts are different in that the burst jet has a high flux directed towards the atmosphere. (That’s when we notice them,) “These extreme electromagnetic events are second only to the Big Bang as the most energetic and luminous phenomenon ever known.” “Earth’s atmosphere is very effective at absorbing high energy electromagnetic radiation such as x-rays and gamma rays, so these types of radiation would not reach any dangerous levels at the surface during the burst event itself. The immediate effect on life on Earth from a GRB within a few kiloparsecs would only be a short increase in ultraviolet radiation at ground level, lasting from less than a second to tens of seconds. This ultraviolet radiation could potentially reach dangerous levels depending on the exact nature and distance of the burst, but it seems unlikely to be able to cause a global catastrophe for life on Earth.[153][154] The long-term effects from a nearby burst are more dangerous. Gamma rays cause chemical reactions in the atmosphere involving oxygen and nitrogen molecules, creating first nitrogen oxide then nitrogen dioxide gas. The nitrogen oxides cause dangerous effects on three levels. …” [Wikipedia]
There is only one mass extinction that has been a suspect for a GRB event causation. “The major Ordovician–Silurian extinction event 450 million years ago may have been caused by a GRB.[14][156]” However, that event was complicated by occurring in pulses, and there is a long list of candidate factors: “glaciation and cooling”, “anoxia and euxinia”, “metal poisoning”, “GRB”, “volcanism”, “asteroid impact”. Any combination of those, or additional unknown factors, could have contributed to the event. Large scale volcanism due to plate tectonic changes is the usual candidate in such lists and for the largest mass extinction in the fossil record (the Permian-Triassic mass extinction) it was the most likely.
how could they watch the gamma Ray burst when it happened 300 years ago? they didn’t see it “just happen”.
3000 years ago
Too bad that the morphology complexity didn’t allow them to better tie down the very high energy gamma emitting region.
On the other hand they got more evidence of the magnetically arrested disk model and saw an accretion disk luminosity maximum that appears to shift with the jet alignment. The latter points to potential influence of the jet on the disk.