We present the first high-precision photometry of the transiting extrasolar planetary system WASP-7 , obtained using telescope defocussing techniques and reaching a scatter of 0.68 mmag per point .
We find that the transit depth is greater and that the host star is more evolved than previously thought .
The planet has a significantly larger radius ( 1.330 \pm 0.093 { R } _ { Jup } versus 0.915 ^ { +0.046 } _ { -0.040 } { R } _ { Jup } ) and much lower density ( 0.41 \pm 0.10 \rho _ { Jup } versus 1.26 ^ { +0.25 } _ { -0.21 } \rho _ { Jup } ) and surface gravity ( 13.4 \pm 2.6 m s ^ { -2 } versus 26.4 ^ { +4.4 } _ { -4.0 } m s ^ { -2 } ) than previous measurements showed .
Based on the revised properties it is no longer an outlier in planetary mass–radius and period–gravity diagrams .
We also obtain a more precise transit ephemeris for the WASP-7 system .