  Thermal emission from Kuiper Belt object (136108) Haumea was measured with
Herschel-PACS at 100 and 160 micrometers for almost a full rotation period.
Observations clearly indicate a 100-micrometer thermal lightcurve with an
amplitude of a factor of ~ 2, which is positively correlated with the optical
lightcurve. This confirms that both are primarily due to shape effects. A
160-micrometer lightcurve is marginally detected. Radiometric fits of the mean
Herschel- and Spitzer- fluxes indicate an equivalent diameter D ~ 1300 km and a
geometric albedo p_v ~ 0.70-0.75. These values agree with inferences from the
optical lightcurve, supporting the hydrostatic equilibrium hypothesis. The
large amplitude of the 100-micrometer lightcurve suggests that the object has a
high projected a/b axis ratio (~ 1.3) and a low thermal inertia as well as
possible variable infrared beaming. This may point to fine regolith on the
surface, with a lunar-type photometric behavior. The quality of the thermal
data is not sufficient to clearly detect the effects of a surface dark spot.
