  Although the environments of star and planet formation are thermodynamically
cold, substantial X-ray emission from 10-100 MK plasmas is present. In low mass
pre-main sequence stars, X-rays are produced by violent magnetic reconnection
flares. In high mass O stars, they are produced by wind shocks on both stellar
and parsec scales. The recent Chandra Orion Ultradeep Project, XMM-Newton
Extended Survey of Taurus, and Chandra studies of more distant high-mass star
forming regions reveal a wealth of X-ray phenomenology and astrophysics. X-ray
flares mostly resemble solar-like magnetic activity from multipolar surface
fields, although extreme flares may arise in field lines extending to the
protoplanetary disk. Accretion plays a secondary role. Fluorescent iron line
emission and absorption in inclined disks demonstrate that X-rays can
efficiently illuminate disk material. The consequent ionization of disk gas and
irradiation of disk solids addresses a variety of important astrophysical
issues of disk dynamics, planet formation, and meteoritics. New observations of
massive star forming environments such as M 17, the Carina Nebula and 30
Doradus show remarkably complex X-ray morphologies including the low-mass
stellar population, diffuse X-ray flows from blister HII regions, and
inhomogeneous superbubbles. X-ray astronomy is thus providing qualitatively new
insights into star and planet formation.

Astrophysics