Study explains decades of black hole observations
A new study by astronomers at NASA, Johns Hopkins University and Rochester Institute of Technology confirms long-held suspicions about how stellar-mass black holes produce their highest-energy light.
"We're accurately representing the real object and calculating the light an astronomer would actually see," says Scott Noble, associate research scientist in RIT's Center for Computational Relativity and Gravitation. "This is a first-of-a-kind calculation where we actually carry out all the pieces together. We start with the equations we expect the system to follow, and we solve those full equations on a supercomputer. That gives us the data with which we can then make the predictions of the X-ray spectrum."
Lead researcher Jeremy Schnittman, an astrophysicist at NASA's Goddard Space Flight Center, says the study looks at one of the most extreme physical environments in the universe: "Our work traces the complex motions, particle interactions and turbulent magnetic fields in billion-degree gas on the threshold of a black hole."
By analyzing a supercomputer simulation of gas flowing into a black hole, the team finds they can reproduce a range of important X-ray features long observed in active black holes.
"We've predicted and come to the same evidence that the observers have," Noble says. "This is very encouraging because it says we actually understand what's going on. If we made all the correct steps and we saw a totally different answer, we'd have to rethink what our model is."
Gas falling toward a black hole initially orbits around it and then accumulates into a flattened disk. The gas stored in this disk gradually spirals inward and becomes compressed and heated as it nears the center. Ultimately reaching temperatures up to 20 million degrees Fahrenheit (12 million C)—some 2,000 times hotter than the sun's surface—the gas shines brightly in low-energy, or soft, X-rays.
For more than 40 years, however, observations show that black holes also produce considerable amounts of "hard" X-rays, light with energy 10 to hundreds of times greater than soft X-rays. This higher-energy light implies the presence of correspondingly hotter gas, with temperatures reaching billions of degrees.
Read more at: http://phys.org/news/
A new study by astronomers at NASA, Johns Hopkins University and Rochester Institute of Technology confirms long-held suspicions about how stellar-mass black holes produce their highest-energy light.
"We're accurately representing the real object and calculating the light an astronomer would actually see," says Scott Noble, associate research scientist in RIT's Center for Computational Relativity and Gravitation. "This is a first-of-a-kind calculation where we actually carry out all the pieces together. We start with the equations we expect the system to follow, and we solve those full equations on a supercomputer. That gives us the data with which we can then make the predictions of the X-ray spectrum."
Lead researcher Jeremy Schnittman, an astrophysicist at NASA's Goddard Space Flight Center, says the study looks at one of the most extreme physical environments in the universe: "Our work traces the complex motions, particle interactions and turbulent magnetic fields in billion-degree gas on the threshold of a black hole."
By analyzing a supercomputer simulation of gas flowing into a black hole, the team finds they can reproduce a range of important X-ray features long observed in active black holes.
"We've predicted and come to the same evidence that the observers have," Noble says. "This is very encouraging because it says we actually understand what's going on. If we made all the correct steps and we saw a totally different answer, we'd have to rethink what our model is."
Gas falling toward a black hole initially orbits around it and then accumulates into a flattened disk. The gas stored in this disk gradually spirals inward and becomes compressed and heated as it nears the center. Ultimately reaching temperatures up to 20 million degrees Fahrenheit (12 million C)—some 2,000 times hotter than the sun's surface—the gas shines brightly in low-energy, or soft, X-rays.
For more than 40 years, however, observations show that black holes also produce considerable amounts of "hard" X-rays, light with energy 10 to hundreds of times greater than soft X-rays. This higher-energy light implies the presence of correspondingly hotter gas, with temperatures reaching billions of degrees.
Read more at: http://phys.org/news/
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