USRA: Magnetic Fields May Be the Key to Black Hole Activity

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USRA: Magnetic Fields May Be the Key to Black Hole Activity

Post by bystander » Sat Oct 20, 2018 4:35 pm

Magnetic Fields May Be the Key to Black Hole Activity
Universities Space Research Association | NASA | Sophia | 2018 Oct 17

Researchers using NASA's SOFIA airborne telescope have found that magnetic fields are trapping the material that feeds the supermassive black hole in the galaxy Cygnus A.

coreofcygnusa_fnl_lynettecook_cf.jpg
Artist’s conception of the core of Cygnus A, including the dusty donut-shaped
surroundings, called a torus, and jets launching from its center. Magnetic fields
are illustrated trapping the dust in the torus. These magnetic fields could be
helping power the black hole hidden in the galaxy’s core by confining the dust in
the torus and keeping it close enough to be gobbled up by the hungry black hole.
Image Credit: NASA/SOFIA/Lynette Cook

Collimated jets provide astronomers with some of the most powerful evidence that a supermassive black hole lurks in the heart of most galaxies. Some of these black holes appear to be active, gobbling up material from their surroundings and launching jets at ultra-high speeds, while others are quiescent, even dormant. Why are some black holes feasting and others starving? Recent observations from the Stratospheric Observatory for Infrared Astronomy, or SOFIA, are shedding light on this question.

SOFIA data indicate that magnetic fields are trapping and confining dust near the center of the active galaxy, Cygnus A, and feeding material onto the supermassive black hole at its center.

The unified model, which attempts to explain the different properties of active galaxies, states that the core is surrounded by a donut-shaped dust cloud, called a torus. How this obscuring structure is created and sustained has never been clear, but these new results from SOFIA indicate that magnetic fields may be responsible for keeping the dust close enough to be devoured by the hungry black hole. In fact, one of the fundamental differences between active galaxies like Cygnus A and their less active cousins, like our own Milky Way, may be the presence or absence of a strong magnetic field around the black hole.

Although celestial magnetic fields are notoriously difficult to observe, astronomers have used polarized light -- optical light from scattering and radio light from accelerating electrons -- to study magnetic fields in galaxies. But optical wavelengths are too short and the radio wavelengths are too long to observe the torus directly. The infrared wavelengths observed by SOFIA are just right, allowing scientists, for the first time, to target and isolate the dusty torus. ...

The Highly Polarized Dusty Emission Core of Cygnus A ~ Enrique Lopez-Rodriguez et al
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