  Pulsars with compact companions in close eccentric orbits are unique
laboratories for testing general relativity and alternative theories of
gravity. Moreover, they are excellent targets for future gravitational wave
experiments like LISA and they are also highly important for understanding the
equation of state of super-dense matter and the evolution of massive binaries.
Here we report on optical observations of the 1.02 M_sun companion to the
pulsar PSR J1141-6545. We detect an optical counterpart with apparent
magnitudes V=25.08(11) and R=24.38(14), consistent with the timing position of
the pulsar. We demonstrate that our results are in agreement with a white dwarf
companion. However the latter is redder than expected and the inferred values
are not consistent with the theoretical cooling tracks, preventing us from
deriving the exact age. Our results confirm the importance of the PSR
J1141-6545 system for gravitational experiments.
