  We present the first coherent dynamical study of the cloud
fragmentation-phase, collapse and early stellar evolution of a solar mass star.
We determine young star properties as the consequence of the parent cloud
evolution. Mass, luminosity and effective temperature in the first million
years of the proto-Sun result from gravitational fragmentation of a molecular
cloud region that produces a cluster of prestellar clumps. We calculate the
global dynamical behavior of the cloud using isothermal 3D hydrodynamics and
follow the evolution of individual protostars in detail using a 1D
radiation-fluid-dynamic system of equations that comprises a correct standard
solar model solution, as a limiting case. We calculate the pre-main sequence
(PMS) evolutionary tracks of a solar mass star in a dense stellar cluster
environment and compare it to one that forms in isolation. Up to an age of
950.000 years differences in the accretion history lead to significantly
different temperature and luminosity evolution. As accretion fades and the
stars approach their final masses the two dynamic PMS tracks converge. After
that the contraction of the quasi-hydrostatic stellar interiors dominate the
overall stellar properties and proceed in very similar ways. Hence the position
of a star in the Hertzsprung-Russell diagram becomes a function of age and mass
only. However, our quantitative description of cloud fragmentation, star
formation and early stellar evolution predicts substantial corrections to the
classical, i.e. hydrostatic and initially fully convective models: At an age of
1 million years the proto-Sun is twice as bright and 500 Kelvin hotter than
according to calculations that neglect the star formation process.
