A Minimum‐Mass Extrasolar Nebula

By analogy with the minimum-mass solar nebula, we construct a surface-density profile using the orbits of the 26 precise-Doppler planets found in multiple-planet systems: Σ = 2200 ( a /1 AU) -β g cm -2 , where a is the circumstellar radius and β = 2.0 ± 0.5. The minimum-mass solar nebula (β = 1.5) is consistent with this model, but the uniform-α accretion disk model (β ≈ 1) is not. In a nebula with β > 2, the center of the disk is the likely cradle of planet formation.