We present the first observational evidence for a circumplanetary disk around the protoplanet PDS 70 b , based on a new spectrum in the K band acquired with VLT/SINFONI .
We tested three hypotheses to explain the spectrum : Atmospheric emission from the planet with either ( 1 ) a single value of extinction or ( 2 ) variable extinction , and ( 3 ) a combined atmospheric and circumplanetary disk model .
Goodness-of-fit indicators favour the third option , suggesting circumplanetary material contributing excess thermal emission — most prominent at \lambda \gtrsim 2.3 \mu m. Inferred accretion rates ( \sim 10 ^ { -7.8 } – 10 ^ { -7.3 } M _ { J } yr ^ { -1 } ) are compatible with observational constraints based on the H \alpha and Br \gamma lines .
For the planet , we derive an effective temperature of 1500–1600 K , surface gravity \log ( g ) \sim 4.0 , radius \sim 1.6 R _ { J } , mass \sim 10 M _ { J } , and possible thick clouds .
Models with variable extinction lead to slightly worse fits .
However , the amplitude ( \Delta A _ { V } \gtrsim 3 mag ) and timescale of variation ( \lesssim years ) required for the extinction would also suggest circumplanetary material .