  We have detected the Rossiter-Mclaughlin effect during a transit of WASP-47b,
the only known hot Jupiter with close planetary companions. By combining our
spectroscopic observations with Kepler photometry, we show that the projected
stellar obliquity is $\lambda = 0^\circ \pm 24^\circ$. We can firmly exclude a
retrograde orbit for WASP-47b, and rule out strongly misaligned prograde
orbits. Low obliquities have also been found for most of the other compact
multiplanet systems that have been investigated. The Kepler-56 system, with two
close-in gas giants transiting their subgiant host star with an obliquity of at
least 45$^\circ$, remains the only clear counterexample.
