Dusty surprise around giant black hole discovered
Washington: New observations of a nearby active galaxy using Very Large Telescope Interferometer (VLTI) at ESO`s Paranal Observatory in Chile have given a team of astronomers a surprise.
It is believed some black holes grow by drawing in matter from their surroundings, creating in the process the most energetic objects in the Universe: active galactic nuclei (AGN).
The central regions of these brilliant powerhouses are ringed by doughnuts of cosmic dust dragged from the surrounding space, similar to how water forms a small whirlpool around the plughole of a sink. It was thought that most of the strong infrared radiation coming from AGN originated in these doughnuts.
Although the hot dust - at some 700 to 1000 degrees Celsius - is indeed in a torus as expected, astronomers observing of the galaxy NGC 3783 using VLTI found huge amounts of cooler dust above and below this main torus.
"This is the first time we`ve been able to combine detailed mid-infrared observations of the cool, room-temperature dust around an AGN with similarly detailed observations of the very hot dust. This also represents the largest set of infrared interferometry for an AGN published yet," explained Sebastian Honig (University of California Santa Barbara, USA and Christian-Albrechts-Universitat zu Kiel, Germany), lead author of the study.
The newly-discovered dust forms a cool wind streaming outwards from the black hole. This wind must play an important role in the complex relationship between the black hole and its environment. The black hole feeds its insatiable appetite from the surrounding material, but the intense radiation this produces also seems to be blowing the material away.
It is still unclear how these two processes work together and allow supermassive black holes to grow and evolve within galaxies, but the presence of a dusty wind adds a new piece to this picture.
These new observations may lead to a paradigm shift in the understanding of AGN. They are direct evidence that dust is being pushed out by the intense radiation. Models of how the dust is distributed and how supermassive black holes grow and evolve must now take into account this newly-discovered effect.
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