NASA's Fermi Telescope finds brightest light sources originate near black holes at galaxy centres.
Fermi spots gamma rays from active galaxies with spinning black hole disks
Photo Credit: NASA
Some of the brightest lights in the universe shine from some of its darkest corners — so-called supermassive black holes. Invisible to the human eye, these high-energy powerhouses light up the cosmos with emissions that are detected by space telescopes. Thousands of such light sources have been discovered with NASA's Fermi Gamma-ray Space Telescope, which has been observing since 2008. These aren't just stars — they are active galactic nuclei (AGN) where large gravitational forces fling matter around black holes, creating intense radiation blasts all across the electromagnetic spectrum.
As per NASA's observational data, black holes lurk at the centres of most galaxies and are hundreds of thousands to billions of times the mass of the sun. In AGN, gas and dust fall into an inward-spiralling disk. Second, the disks experience friction and magnetic forces that produce light from radio to gamma rays.
About one in ten AGN produce powerful jets of particles that move at nearly the speed of light, and it's still a mystery to scientists how material so close to the event horizon is accelerated in the jets.
Interestingly, the type of AGN observed depends on its orientation relative to Earth.
Radio galaxies shoot their jets sideways, while blazars aim them nearly straight at us, making them appear especially bright in gamma rays. Fermi's sky surveys show that more than half of the thousands of gamma-ray sources it has recorded are blazars, giving researchers vital clues about the energetic mechanics behind these cosmic light shows.
AGN are more than just bright; scientists are attracted to them for what they tell us about cosmic history. AGN existed in the early universe and were probably important in modulating galaxy evolution. Astrophysicists will use observations and analyses of the conditions directly around these black holes to learn more about the structure and history of the universe itself.
The paradox is acute: black holes are famous for eating up all the light and matter they can latch onto, but they lie behind some of the most luminous phenomena seen in space. Through missions like Fermi, scientists are adjusting the picture of the universe, in which some of its darkest origins can sparkle the most.
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