We analyze new/archival VLT/NaCo and Gemini/NICI high-contrast imaging of the young , self-luminous planet \beta Pictoris b in seven near-to-mid IR photometric filters , using advanced image processing methods to achieve high signal-to-noise , high precision measurements .
While \beta Pic b ’ s near-IR colors mimick that of a standard , cloudy early-to-mid L dwarf , it is overluminous in the mid-infrared compared to the field L/T dwarf sequence .
Few substellar/planet-mass objects – i.e . \kappa And b and 1RXJ 1609B – match \beta Pic b ’ s JHK _ { s } L ^ { \prime } photometry , and its 3.1 \mu m and 5 \mu m photometry are particularly difficult to reproduce .
Atmosphere models adopting cloud prescriptions and large ( \sim 60 \mu m ) dust grains fail to reproduce the \beta Pic b spectrum .
However , models incorporating thick clouds similar to those found for HR 8799 bcde but also with small ( a few microns ) modal particle sizes yield fits consistent with the data within uncertainties .
Assuming solar abundance models , thick clouds , and small dust particles ( < a > = 4 \mu m ) we derive atmosphere parameters of log ( g ) = 3.8 \pm 0.2 and T _ { eff } = 1575–1650 K , an inferred mass of 7 ^ { +4 } _ { -3 } M _ { J } , and a luminosity of log ( L/L _ { \odot } ) \sim -3.80 \pm 0.02 .
The best-estimated planet radius , \approx 1.65 \pm 0.06 R _ { J } , is near the upper end of allowable planet radii for hot-start models given the host star ’ s age and likely reflects challenges with constructing accurate atmospheric models .
Alternatively , these radii are comfortably consistent with hot-start model predictions if \beta Pic b is younger than \approx 7 Myr , consistent with a late formation , well after its host star ’ s birth \sim 12 ^ { +8 } _ { -4 } Myr ago .