  The six planets of the Kepler-11 system are the archetypal example of a
population of surprisingly low-density transiting planets revealed by the
Kepler mission. We have determined the fundamental parameters and chemical
composition of the Kepler-11 host star to unprecedented precision using an
extremely high quality spectrum from Keck-HIRES (R$\simeq$67,000, S/N per
pixel$\simeq$260 at 600 nm). Contrary to previously published results, our
spectroscopic constraints indicate that Kepler-11 is a young main-sequence
solar twin. The revised stellar parameters and new analysis raise the densities
of the Kepler-11 planets by between 20-95% per planet, making them more typical
of the emerging class of "puffy" close-in exoplanets. We obtain photospheric
abundances of 22 elements and find that Kepler-11 has an abundance pattern
similar to that of the Sun with a slightly higher overall metallicity. We
additionally analyze the Kepler lightcurves using a photodynamical model and
discuss the tension between spectroscopic and transit/TTV-based stellar density
estimates.
