Detonating Accretion Disks

An accretion disk is the plane of matter that surrounds an very massive object, held there by its gravitational field. Stars that are somewhere in the range of our Sun’s mass are believed to form by accretion, the repeated layering of matter onto the sun from its disk. The other major theory is that these stars coalesce from multiple minor stars and this theory is still not disproven but there is now considerable evidence for the other side. When gravitational torques and general instability form within the disk it is possible for the outer layers of the disk to fall in and the whole system to speed up. This transports mass towards the sun at the centre as angular momentum is moved to the outside of the spinning ring. This process is called an accretion burst and it is plausible that this effect could occur at a range of temperatures, densities and angular speeds. The new discovery is an observation, the first of its kind to see accretion burst from a stars disk. The star in particular was twenty times the mass of our Sun and when the energy outputs were compared to a protostar’s turbulent burst the difference was extreme. The luminosity, the energy released and the accretion rate were over one hundred times greater then the accretion bursts in small stars without disks. It can be concluded that these periodic bursts of activity are the primary method of stars gaining mass across a wide range of sizes and types.

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