Stellar spin-orbit misalignment
In the Solar system, the planets follow orbits that are nearly aligned with the Sun's equatorial plane. What about planets around other stars? Many techniques are available to measure the obliquities of planet-hosting stars, ranging from an effect predicted in the 19th century to several techniques relying on precise photometry that can only be obtained with space telescopes. Many exoplanetary systems show good alignment, but we have also found planets on highly inclined and retrograde orbits. I will review what we have learned from these measurements, with particular attention to two recent results: an apparent preference for polar orbits, and statistical constraints on the obliquity distribution of Kepler stars.