ASTRONOMY COLLOQUIUM - FEBRUARY 21, 2006
Eric Feigelson, Penn State
What are X-rays Telling Us About Star and Planet Formation?
X-ray studies have established that low-mass stars exhibit their
highest levels of magnetic activity during their pre-main sequence
phases when planet formation occurs. Our understanding of this
activity, and particularly violent magnetic reconnection flares, has
been greatly advanced by recent studies such as the Chandra Orion
Ultradeep Project (COUP). COUP provides several lines of evidence
that X-rays efficiently illuminate the 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 address
long-standing meteoritic issues such as the production of short-lived
radionuclides and the flash melting of chondrules. We conclude that
solar systems form in cool dark disks which are likely irradiated by
108 violent magnetic reconnection flare events.