  Historically, variable and transient sources have both surprised astronomers
and provided new views of the heavens. Here we report the discovery of an
optical transient in the outskirts of the lenticular galaxy Messier 85 in the
Virgo Cluster. With a peak absolute R magnitude of -12 this event is distinctly
brighter than novae, but fainter than type Ia supernovae (expected from a
population of old stars in lenticular galaxies). Archival images of the field
do not show a luminous star at that position with an upper limit of ~-4.1, so
it is unlikely to be a giant eruption from a luminous blue variable star. Over
a two month period the transient emitted radiation energy of almost 10E47 erg
and subsequently faded in the opical sky. It is similar to, but more luminous
at peak by a factor of 6 than, an enigmatic transient in the galaxy M31. A
possible origin of M85 OT2006-1 is a stellar merger. If so, searches for
similar events in nearby galaxies will not only allow to study the physics of
hyper-Eddington sources, but also probe an important phase in the evolution of
stellar binary systems.
