We report the discovery and characterisation of WASP-180Ab , a hot Jupiter confirmed by the detection of its Doppler shadow and by measuring its mass using radial velocities .
We find the 0.9 \pm 0.1 M _ { Jup } , 1.24 \pm 0.04 R _ { Jup } planet to be in a misaligned , retrograde orbit around an F7 star with T _ { eff } = 6500 K and a moderate rotation speed of v \sin i _ { \star } = 19.9 km s ^ { -1 } .
The host star is the primary of a V = 10.7 binary , where a secondary separated by \sim 5 ^ { \prime \prime } ( \sim 1200 AU ) contributes \sim 30 % of the light .
WASP-180Ab therefore adds to a small sample of transiting hot Jupiters known in binary systems .
A 4.6-day modulation seen in the WASP data is likely to be the rotational modulation of the companion star , WASP-180B .