Last April, after having traveled halfway across the universe, a powerful cascade of gamma rays was observed, allowing astronomers to see a major black hole eruption like never before.
Two teams of astronomers were able to use different instrumentation to piece together a huge amount of information about galaxy PKS 1441+25, which is 7.6 billion light-years away. The supermassive black hole at its center has a mass of 70 million suns, with an event horizon (the surface of no return around a black hole) with a radius of over 300 million kilometers (190 million miles).
The findings from the MAGIC team and VERITAS team are both published in The Astrophysical Journal Letters.
PKS 1441+25 is so bright in gamma rays because it’s a blazar: The direction of the black hole jets are aligned to our line-of-sight. Due to the favorable alignment between Earth and the galaxy, the researchers were able to discover the surprising neighborhood of the supermassive black hole.
"When we looked at all the data from this event, from gamma rays to radio, we realized the measurements told us something we didn't expect about how the black hole produced this energy," Jonathan Biteau, co-author of one of the papers that reported these findings, said in a statement.
It was thought that different regions would produce light at different energies, with the most powerful gamma rays produced very close to the event horizon.
"Instead, the multiwavelength picture suggests that light at all wavelengths came from a single region located far away from the power source," Biteau explained.
Biteau and his team were able to make this discovery using the results from the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The other team used NASA’s Fermi telescope and the Major Atmospheric Gamma-ray Imaging Cerenkov experiment (MAGIC), located on La Palma in the Canary Islands.
The MAGIC team was able to measure the energy of the gamma rays emitted and they discovered that PKS 1441+25 is a powerhouse. The gamma rays measured reached the highest detection limit, each photon being between 20 and 125 billion times more energetic than a ray of sunlight.
"Because this galaxy is so far away, we didn't have a strong expectation of detecting gamma rays with energies this high," said Josefa Becerra Gonzalez, a researcher who analyzed data as part of the MAGIC study. "There are fewer and fewer gamma rays at progressively higher energies, and fewer still from very distant sources."
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