Dust Dispersion Around a Black Hole Surprises Astronomers

While observing the material around the black hole in the center of the NGC 3783 galaxy, astronomers have found out that the way the dust surrounds the black hole is in conflict with accepted theories on these massive objects.

Artist impression of the black hole in the center of NGC 3783 galaxy.

Artist impression of the black hole in the center of NGC 3783 galaxy.

Some may argue that black holes are not real, that they are just a theory. We can't see them directly because even the light can't escape their gravitational pull, but there is strong circumstantial evidence supporting their existence. We are talking about the effects that black holes have on surrounding objects like stars, light from the stars behind the black hole, dust and gas. Many galaxies have supermassive black holes in their center and current theories describe the surrounding area as a torus, or a doughnut, made of gas and dust.

An observation of the NGC 3783 galaxy suggests that the dust surrounding supermassive black hole in the center of this galaxy is found both above and below the dust forming a doughnut. This is something that surprised the team of astronomers, led by Sebastian Hönig of the University of California, Santa Barbara, USA and the University of Kiel in Germany. Their observations, made by using the European Southern Observatory's Very Large Telescope Interferometer in Chile, suggest that while the black hole feeds on the surrounding material, releasing powerful radiation mainly in the X-ray spectrum, it also pushes some of this material outward.

This could prove important in understanding how massive black holes in centers of galaxies work. The gas and dust inside the doughnut are hot, with temperatures between 700 and 1000 degrees Celsius, but the dust around the doughnut has cooled down. "This is the first time we’ve been able to combine detailed mid-infrared observations of the cool, room-temperature dust around an active galactic nucleus with similarly detailed observations of the very hot dust," Hönig said in a statement.

In order to even better understand supermassive black holes, a new instrument called Matisse is being developed for the VLT Interferometer. It will allow astronomers to combine light from all four separate telescopes at once, thus allowing much more detailed data. Four VLT's Unit Telescopes operate as independent telescopes, combining the light from multiple telescopes (interferometry) only about 20 percent of the time.

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