Optically thin dust-mass estimator ($M_d=F_{\nu }{D}^2/[{\kappa }_{\nu }{B}_{\nu }(T)]$)

For isothermal optically thin dust at distance $D$, its measured spectral flux density determines its mass through $M_d=F_{\nu }{D}^2/[{\kappa }_{\nu }{B}_{\nu }(T)]$. Temperature and opacity uncertainty commonly dominate the inferred mass uncertainty.