Black holes and ice skaters

Black holes and ice skaters

Jan 01, 2019 / By : / Category : 老域名购买

Black holes pose a bit of a mystery in some respects. One such mystery is the disk of matter that accumulates and spirals into the whole, called an accretion disk. The fundamental problem in understanding such a disk is that measurements show that angular momentum is lost as matter moves closer to the black hole before falling in. If angular momentum were not lost the matter closer in to the black hole would rotate much faster than measured, like the spinning ice skater that draws in their arms. In terms of a fluid, we would say that the disk had some viscosity, however, in fluids viscosity is essentially a product of collisions. Unfortunately, the density of accretion disks rule out collisions and gravity being the only significant mechanisms for removing angular momentum. 老域名出售

Now observations performed with the Chandra X-ray observatory have shed some light on where the angular momentum goes. The researchers observed a black hole with an accretion disk that was oriented edgewise towards us. This allowed the researchers to observe which species were in the disk and their tangential speed. They found that the disk is mainly composed of ions, which, as they orbit the black hole, generate a strong magnetic field. This magnetic field generates friction in the disk, which looks a bit like wind, slowing the circulating matter, destabilizing the orbit and allowing it to fall into the black hole.

Although these observations don't eliminate every other possible mechanism for slowing the rate of spin, their measurements show that the maximum amount of angular momentum removed by the magnetically generated wind is in very good agreement with the amount of angular momentum loss observed. However, since the disk is not exactly edge on to us, it is likely that the magnetic wind is not quite sufficient.

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