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A study conducted by NASA’s Chandra X-ray observatory has revealed that black holes are the most fuel-efficient engines in the Universe. Black holes generate energy and affect their environment, the study said, adding that most of the energy released by matter falling toward a supermassive black hole was in the form of high-energy jets travelling at near the speed of light away from the black hole. "This is an important step in understanding how such jets can be launched from magnetised disks of gas near the event horizon of a black hole. Just as with cars, it’s critical to know the fuel efficiency of black holes," said lead author Steve Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, and the Stanford Linear Accelerator Center. "Without this information, we cannot figure out what is going on under the hood, so to speak, or what the engine can do," he said. Allen and his team used Chandra to study nine supermassive black holes at the centres of elliptical galaxies. These black holes are relatively old and generate much less radiation than quasars, rapidly growing supermassive black holes seen in the early Universe. To their surprise, Allen and his team found that these "quiet" black holes were all producing much more energy in jets of high-energy particles than in visible light or X-rays. These jets created huge bubbles, or cavities, in the hot gas in the galaxies. The researchers calculated the efficiency of the black hole energy production in two steps. First the Chandra images of the inner regions of the galaxies were used to estimate how much fuel was available for the black hole and then they were used to estimate the power required to produce the cavities. "If a car was as fuel-efficient as these black holes, it could theoretically travel over a billion miles on a gallon of gas," said co-author Christopher Reynolds of the University of Maryland, College Park. "These black holes are very efficient, but it also takes a very long time to refuel them," Allen added. Researchers said the new study showed that black holes were green in another important way. The energy transferred to the hot gas by the jets kept hot gas from cooling, thereby preventing billions of new stars from forming. This will place limits on the growth of the largest galaxies, and prevent galactic sprawl from taking over the neighborhood, they said. They further said that the new study also showed that matter flowed towards the black holes at a steady rate for several million years. — ANI
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