  On 19 March 2008, the northern sky was the stage of a spectacular optical
transient that for a few seconds remained visible to the naked eye. The
transient was associated with GRB 080319B, a gamma-ray burst at a luminosity
distance of about 6 Gpc (standard cosmology), making it the most luminous
optical object ever recorded by human kind. We present comprehensive sky
monitoring and multi-color optical follow-up observations of GRB 080319B
collected by the RAPTOR telescope network covering the development of the
explosion and the afterglow before, during, and after the burst. The extremely
bright prompt optical emission revealed features that are normally not
detectable. The optical and gamma-ray variability during the explosion are
correlated, but the optical flux is much greater than can be reconciled with
single emission mechanism and a flat gamma-ray spectrum. This extreme optical
behavior is best understood as synchrotron self-Compton model (SSC). After a
gradual onset of the gamma-ray emission, there is an abrupt rise of the prompt
optical flux suggesting that variable self-absorption dominates the early
optical light curve. Our simultaneous multi-color optical light curves
following the flash show spectral evolution consistent with a rapidly decaying
red component due to large angle emission and the emergence of a blue forward
shock component from interaction with the surrounding environment. While
providing little support for the reverse shock that dominates the early
afterglow, these observations strengthen the case for the universal role of the
SSC mechanism in generating gamma-ray bursts.
