We present observations of the Rossiter-McLaughlin effect for two
exoplanetary systems, revealing the orientations of their orbits relative to
the rotation axes of their parent stars. HAT-P-4b is prograde, with a
sky-projected spin-orbit angle of lambda = -4.9 +/- 11.9 degrees. In contrast,
HAT-P-14b is retrograde, with lambda = 189.1 +/- 5.1 degrees. These results
conform with a previously noted pattern among the stellar hosts of close-in
giant planets: hotter stars have a wide range of obliquities and cooler stars
have low obliquities. This, in turn, suggests that three-body dynamics and
tidal dissipation are responsible for the short-period orbits of many
exoplanets. In addition, our data revealed a third body in the HAT-P-4 system,
which could be a second planet or a companion star.Comment: AJ, in press [8 pages
