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Black hole spin cranks-up radio volume

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Black hole spin cranks-up radio volume

Post by Dragon on Fri Jan 19, 2018 6:39 pm

Statistical analysis of supermassive black holes suggests that the spin of the black hole may play a role in the generation of powerful high-speed jets blasting radio waves and other radiation across the universe.

Black holes absorb light and all other forms of radiation, making them impossible to detect directly. But the effects of black holes, in particular accretion disks where matter is shredded and superheated as it spirals down into the black hole, can release enormous amounts of energy. The accretion disks around supermassive black holes (black holes with masses millions of times that of the sun) are some of the brightest objects in the universe. These objects are called "quasi-stellar radio sources" or "quasars," but actually this is a misnomer; only about 10% of quasars emit strong radio waves. We now know that "radio loud" quasars occur when a fraction of the matter in the accretion disk avoids the final fate of falling into the black hole and comes blasting back out into space in high-speed jets emitted from the poles of the black hole. But we still don't understand why jets form some times and not other times.

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Re: Black hole spin cranks-up radio volume

Post by Dragon on Fri Jan 19, 2018 6:40 pm


. Credit: NAOJ

Artist's conception of the accretion disk around a spinning super-massive black hole. The rotation of the black hole may cause the high-speed jet which makes the object radio-loud.

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Re: Black hole spin cranks-up radio volume

Post by Dragon on Fri Jan 19, 2018 6:41 pm



This video clip compares the effects on emission lines of spinning and non-spinning black holes.

The video first shows the non-spinning black hole. The accretion disk rotates around the black hole. Note that there is a gap between the inner edge of the accretion disk and the black hole itself. The graph at the bottom shows the shape of the emission from the disk.

The video then shows a spinning black hole. Again the accretion disk rotates around the black hole. Note that disk comes closer to the black hole. The graph at the bottom shows the shape of the emission line.

The animation ends with a side-by-side comparison of the non-spinning and the spinning black holes. The emission from the spinning black hole is less intense than from the non-spinning black hole. It is also spread out over a wider energy range. The rotation of the black hole allows for gas in the disk to get closer. This gas is subjected to a stronger gravitational redshift and higher velocities. These two effects spread the the line over a larger energy range.

 
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