Date:
Tue, 31/12/202412:30-13:30
Speaker: Jonathan Katz (Dept. of Physics, Washington U. in St. Louis, MO, USA)
Title: Star and planet formation and cosmic ray viscosity
Abstract:
The fraction of planetary mass objects in the Trapezium cluster that are in wide binaries is much greater than implied by extrapolation to lower masses of the fraction of stars that are in wide binaries. In a uniform medium with uniform vorticity the collapse criterion is independent of the size and mass of the collapsing region, which would imply a wide binary fraction independent of mass, in contradiction to observation. Angular momentum, rather than thermal energy (the Jeans criterion), may be the chief obstacle to star formation. The excess of Jupiter Mass Binary Objects in the Trapezium cluster may be attributed to cosmic ray viscosity that transports angular momentum to surrounding material. Viscosity is more effective in smaller and less massive collapsing regions, preferentially producing planetary mass wide binaries. Energetic particles trapped on magnetic field lines in a corona contribute to viscosity, dissipation and angular momentum flow in accretion discs.
Zoom link:
https://huji.zoom.us/j/81989505874?pwd=vIU5zHP0HRxEmu7Awp8Lq4xIao7LCL.1
Meeting ID: 819 8950 5874
Passcode: 095544
Contact: Tsvi Piran
Title: Star and planet formation and cosmic ray viscosity
Abstract:
The fraction of planetary mass objects in the Trapezium cluster that are in wide binaries is much greater than implied by extrapolation to lower masses of the fraction of stars that are in wide binaries. In a uniform medium with uniform vorticity the collapse criterion is independent of the size and mass of the collapsing region, which would imply a wide binary fraction independent of mass, in contradiction to observation. Angular momentum, rather than thermal energy (the Jeans criterion), may be the chief obstacle to star formation. The excess of Jupiter Mass Binary Objects in the Trapezium cluster may be attributed to cosmic ray viscosity that transports angular momentum to surrounding material. Viscosity is more effective in smaller and less massive collapsing regions, preferentially producing planetary mass wide binaries. Energetic particles trapped on magnetic field lines in a corona contribute to viscosity, dissipation and angular momentum flow in accretion discs.
Zoom link:
https://huji.zoom.us/j/81989505874?pwd=vIU5zHP0HRxEmu7Awp8Lq4xIao7LCL.1
Meeting ID: 819 8950 5874
Passcode: 095544
Contact: Tsvi Piran