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Wednesday 09 Dec 2009: X-ray insights into star and planet formation
Prof. Eric Feigelson - Penn State University, USA
Physics, 124 11:00-12:00
Observational X-ray studies, such as the Chandra Orion Ultradeep Project, have established that low-mass stars exhibit their highest levels of magnetic activity during their pre-main sequence (PMS) phases. The emission is dominated by flares similar to, but far more powerful and frequent than, contemporary solar flares. As X-ray flaring is present both during and after the era of protoplanetary disks and planet formation, X-ray selection is particularly effective in finding disk-free (Class III) PMS stars. X-ray surveys thus provide rich and disk-unbiased samples of young stellar populations valuable for star formation studies: IMFs, rich cluster structure, triggered star formation, and more. It is also likely that X-rays efficiently illuminate and (slightly) ionize the largely-neutral protoplanetary disks. This may have dramatically affect disk gases: induction of MHD turbulence via the MRI instability with subsequent suppression of protoplanetary migration, heating of disk outer layers, catalysis of nonequilibrium chemistry, and so forth. Flare effects on disk solids may address long-standing meteoritic issues such as the production of short-lived radionuclides and the flash melting of chondrules. Planetary systems form in cool dark disks which are likely irradiated by millions of violent magnetic reconnection flare events.
