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Gaps imaged in protoplanetary discs are suspected to be opened by planets. Wecompute the present-day mass accretion rates $\dot{M}_{\rm p}$ of sevenhypothesized gap-embedded planets, plus the two confirmed planets in the PDS 70disc. The accretion rates are based on disc gas surface densities $\Sigma_{\rmgas}$ from C$^{18}$O observations, and planet masses $M_{\rm p}$ fromsimulations fitted to observed gaps. Assuming accretion is Bondi-like, we findin eight out of nine cases that $\dot{M}_{\rm p}$ is consistent with thetime-averaged value given by the current planet mass and system age, $M_{\rmp}/t_{\rm age}$. As system ages are comparable to circumstellar disc lifetimes,these gap-opening planets may be undergoing their last mass doublings, reachingfinal masses of $M_{\rm p} \sim 10-10^2 \, M_\oplus$ for the non-PDS 70planets, and $M_{\rm p} \sim 1-10 \, M_{\rm J}$ for the PDS 70 planets. Foranother fifteen gaps without C$^{18}$O data, we predict $\Sigma_{\rm gas}$ byassuming their planets are accreting at their time-averaged $\dot{M}_{\rm p}$.Bondi accretion rates for PDS 70b and c are orders of magnitude higher thanaccretion rates implied by measured U-band and H$\alpha$ fluxes, suggestingmost of the accretion shock luminosity emerges in as yet unobserved wavebands,or that the planets are surrounded by dusty, highly extincting, quasi-sphericalcircumplanetary envelopes. Thermal emission from such envelopes or fromcircumplanetary discs, on Hill sphere scales, peaks at wavelengths in themid-to-far-infrared and can reproduce observed mm-wave excesses.

Testing planet formation from the ultraviolet to the millimeter