We report the discovery of two transiting planetary systems : a super dense , sub-Jupiter mass planet WASP-86b ( M _ { pl } = 0.82 \pm 0.06 M _ { J } ; R _ { pl } = 0.63 \pm 0.01 R _ { J } ) , and a bloated , Saturn-like planet WASP-102b ( M _ { pl } = 0.62 \pm 0.04 M _ { J } ; R _ { pl } = 1.27 \pm 0.03 R _ { J } ) .
They orbit their host star every \sim 5.03 , and \sim 2.71 days , respectively .
The planet hosting WASP-86 is a F7 star ( T _ { eff } = 6330 \pm 110 K , [ Fe/H ] = + 0.23 \pm 0.14 dex , and age \sim 0.8–1 Gyr ) ; WASP-102 is a G0 star ( T _ { eff } = 5940 \pm 140 K , [ Fe/H ] = - 0.09 \pm 0.19 dex , and age \sim 1 Gyr ) .
These two systems highlight the diversity of planetary radii over similar masses for giant planets with masses between Saturn and Jupiter .
WASP-102b shows a larger than model-predicted radius , indicating that the planet is receiving a strong incident flux which contributes to the inflation of its radius .
On the other hand , with a density of \rho _ { pl } = 3.24 \pm 0.3 \rho _ { J } , WASP-86b is the densest gas giant planet among planets with masses in the range 0.05 < M _ { pl } < 2.0 M _ { J } .
With a stellar mass of 1.34 M _ { \odot } and [ Fe/H ] = + 0.23 dex , WASP-86 could host additional massive and dense planets given that its protoplanetary disc is expected to also have been enriched with heavy elements .
In order to match WASP-86b ’ s density , an extrapolation of theoretical models predicts a planet composition of more than 80 % in heavy elements ( whether confined in a core or mixed in the envelope ) .
This fraction corresponds to a core mass of approximately 210M _ { \oplus } for WASP-86b ’ s mass of M _ { pl } \sim 260 M _ { \oplus } .
Only planets with masses larger than about 2 M _ { J } have larger densities than that of WASP-86b , making it exceptional in its mass range .