Galaxy 1068 can be seen in close-up in this view from NASA’s Hubble Space Telescope. NuSTAR’s high-energy X-rays eyes were able to obtain the best view yet into the hidden lair of the galaxy’s central, supermassive black hole. Credit: NASA/JPL-Caltech
The most massive black holes in the universe are often encircled by thick, doughnut-shaped disks of gas and dust. This deep-space doughnut material ultimately feeds and nourishes the growing black holes tucked inside. Until recently, telescopes weren’t able to penetrate some of these doughnuts,ie tori.
“Originally, we thought that some black holes were hidden behind walls or screens of material that could not be seen through,” said Andrea Marinucci of the Roma Tre University in Italy. With its X-ray vision, NuSTAR recently peered inside one of the densest of these doughnuts known to surround a supermassive black hole. This black hole lies at the center of a well-studied spiral galaxy NGC 1068, 47M light-years away in Cetus constellation.The observations revealed a clumpy, cosmic doughnut. “The rotating material is not a simple, rounded doughnut as originally thought, but clumpy,” said Marinucci.
Doughnut-shaped disks of gas and dust around supermassive black holes were first proposed in the mid-1980s to explain why some black holes are hidden behind gas and dust, while others are not. The idea is that the orientation of the doughnut relative to Earth affects the way we perceive a black hole and its intense radiation. If the doughnut is viewed edge-on, the black hole is blocked. If the doughnut is viewed face-on, the black hole and its surrounding, blazing materials can be detected. This idea is referred to as the unified model because it neatly joins together the different black hole types, based solely upon orientation.
The new discovery is the first time clumpiness has been observed in an ultra-thick doughnut, and supports the idea that this phenomenon may be common. The research is important for understanding the growth and evolution of massive black holes and their host galaxies.
Both NuSTAR and XMM-Newton observed the supermassive black hole in NGC 1068 simultaneously on two occasions between 2014 to 2015. On one of those occasions, in August 2014, NuSTAR observed a spike in brightness. NuSTAR observes X-rays in a higher-energy range than XMM-Newton, and those high-energy X-rays can uniquely pierce thick clouds around the black hole. The scientists say the spike in high-energy X-rays was due to a clearing in the thickness of the material entombing the supermassive black hole.
The team says that future research will address the question of what causes the unevenness in doughnuts. It’s possible that a black hole generates turbulence as it chomps on nearby material. Or, the energy given off by young stars could stir up turbulence, which would then percolate outward through the doughnut. Another possibility is that the clumps may come from material falling onto the doughnut. As galaxies form, material migrates toward the center, where the density and gravity is greatest. The material tends to fall in clumps, almost like a falling stream of water condensing into droplets as it hits the ground.
http://www.jpl.nasa.gov/news/news.php?feature=4798
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