Title: The Formation of Massive Stars

Speaker: Dr. Richard Klein
Astronomy Department, UC Berkeley

Date: April 6th, 2007

Time: 1:30 - 2:30 pm

Location: San Diego Supercomputer Center, Auditorium
(Direction to SDSC : http://www.sdsc.edu/about/Visitorinfo.html)

Abstract: The formation of massive stars remains one of the most significant unsolved problems in astrophysics, with implications for the formation of the elements and the structure and evolution of galaxies. It is these stars, with masses greater than 8-10 solar masses, that eventually explode as supernovae and produce most of the heavy elements in the universe. These stars dominate the energy injection into the interstellar medium of galaxies through supernovae, stellar winds, and UV radiation. By injecting both heavy elements and energy into the surrounding medium, massive stars shape the evolution of galaxies. Despite the importance of massive star formation, relatively little is known about them theoretically as they pose a major theoretical challenge. These stars begin burning their nuclear fuel and radiating enormous amounts of energy while still accreting gas. For massive stars greater than 10 solar masses, the luminosity can approach the Eddington limit, at which the radiative acceleration from radiation pressure due dust opacity can greatly exceed that of gravity. This leads to a fundamental problem: How is it possible to sustain a sufficiently high mass accretion rate into a protostellar core despite the radiation pressure on the accreting envelope? I will discuss our recent work on the first 3D simulations of massive star formation. Using our high resolution 3D radiation-hydrodynamic adaptive mesh refinement code ORION with a relativistically correct treatment of the radiation transport, we have investigated the formation of high mass stars from both smooth and turbulent initial conditions in the collapsing massive core. I will discuss our work on identifying 2 new mechanisms that efficiently solve the problem of the Eddington barrier to high mass star formation; the presence of 3D Rayleigh Taylor instabilities in radiation driven bubbles present in the accreting envelope and the presence of protostellar outflows providing radiation an escape mechanism from the accreting envelope.

Brief biography: Klein has pioneered methods of radiative transfer and adaptive mesh refinement applied to computational astrophysics over the last several decades with particular application to star formation. He played a central role in the development of the radiation-driven implosion model for induced star formation and in developing the leading theory of stellar winds for hot stars. He founded the Berkeley Astrophysical Fluid Dynamics group with Chris McKee. He also leads a research group in developing scaled laboratory laser astrophysical experiments.