  Short-period planets exhibit day-night temperature contrasts of hundreds to
thousands of degrees K. They also exhibit eastward hotspot offsets whereby the
hottest region on the planet is east of the substellar point; this has been
widely interpreted as advection of heat due to eastward winds. We present
thermal phase observations of the hot Jupiter CoRoT-2b obtained with the IRAC
instrument on the Spitzer Space Telescope. These measurements show the most
robust detection to date of a westward hotspot offset of 23 $\pm$ 4 degrees, in
contrast with the nine other planets with equivalent measurements. The peculiar
infrared flux map of CoRoT-2b may result from westward winds due to
non-synchronous rotation magnetic effects, or partial cloud coverage, that
obscures the emergent flux from the planet's eastern hemisphere.
Non-synchronous rotation and magnetic effects may also explain the planet's
anomalously large radius. On the other hand, partial cloud coverage could
explain the featureless dayside emission spectrum of the planet. If CoRoT-2b is
not tidally locked, then it means that our understanding of star-planet tidal
interaction is incomplete. If the westward offset is due to magnetic effects,
our result represents an opportunity to study an exoplanet's magnetic field. If
it has Eastern clouds, then it means that our understanding of large-scale
circulation on tidally locked planets is incomplete.
