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Astro & GW Colloquium

Protostars and discs: Low-mass star formation in a magnetised medium

Speaker: Dr James Wurster (University of Exeter)
Date: Wednesday 17 October 2018
Time: 14:00
Venue: Trevithick Building T/2.09

Star formation is one of the fundamental processes in the Universe. Stars are born in and shape the evolution of giant molecular clouds, which then may influence the evolution of the gas and dust in their host galaxy. Discs form around young stars, and it is in these discs that planets form. Stars emit the visible light that we see in galaxies, thus understanding their numbers, luminosities and ages is necessary to determine the properties about their host galaxy. Until recently, numerical simulations of low-mass star formation have been unable to produce large discs around a forming protostar. This contradicts observations. With the inclusion of non-ideal magnetohydrodynamics (MHD), large discs are now being formed in numerical simulations, indicating the necessity of non-ideal MHD. However, the outcome is somewhat dependent on initial conditions and free parameters, indicating the necessity of carefully choosing realistic parameters. Finally, if the inclusion of non-ideal MHD can self-consistently re-introduce discs, then what effect will it have on the formation of the protostar itself? In this talk, I will first introduce the history of star formation, ideal MHD, and the three non-ideal MHD processes: Ohmic resistivity, ambipolar diffusion, and the Hall effect. I will then present the results from our numerical smoothed-particle hydrodynamics simulations of protostar formation, focusing on the effect that non-ideal MHD has on the formation of discs, outflows, and on the evolution of the first and second hydrostatic cores themselves.