VIRTUAL

 

Thursday, October 14th    2021

3:45 – 4:45 pm (MT)

WEBEX


Speaker:  Prof. Mitchell Begelman

 

 Distinguished Professor of Astrophysical and Planetary Sciences

Fellow of JILA, at the University of Colorado Boulder

 

“Black Holes and Their Accretion Disks: A Magnetic Perspective”

 

 

Abstract: 

Standard accretion disk theory does a pretty good job of explaining the overall energetics of gas draining into black holes, but it fails in most other respects.  It underpredicts disk thicknesses, inflow speeds and temperatures; predicts violent instabilities that are not seen; and implies that matter feeding the monster black holes in quasars should instead fragment and form stars, leaving the black hole nearly dormant.  The problem seems to be that the theory underestimates the effects of organized magnetic fields on disk structure.  I will discuss how a relatively weak magnetic field, threading the disk, can get amplified so much that it puffs the disk up, utterly changing its structure and potentially resolving the problems mentioned above.

 

Bio: 

Mitchell Begelman is a Distinguished Professor of Astrophysical and Planetary Sciences and a Fellow of JILA, at the University of Colorado Boulder.  He works on a wide range of topics in theoretical astrophysics, including astrophysical fluids and plasmas, high-energy astrophysics, formation and astrophysics of black holes, accretion processes, galaxy formation and evolution, and interstellar and intergalactic matter.   In addition to his research publications he has written two books for a general readership including Gravity's Fatal Attraction: Black Holes in the Universe (with Martin Rees), which won the 1996 American Institute of Physics Science Writing Award and is now in its 3rd edition. He received his Ph.D. from the University of Cambridge and has won a number of awards and fellowships including a Guggenheim Fellowship, a Sloan Research Fellowship, and the American Astronomical Society Warner Prize.