Radiation Pressure Blow-Out Size for Silicate and Carbonaceous Grains

This paper examines Smallest grain sizes that remain bound to the Sun for three compositions, from the radiation-pressure to gravity ratio. Using only published input values and transparent formulae, the calculation obtains the following headline results: blowout_radius_um_silicate_rho2_5 = 0.459; blowout_radius_um_carbon_rho1_8 = 0.638; blowout_radius_um_porous_rho0_8 = 1.435; beta_critical_circular_orbit = 0.5; beta_10um_silicate = 0.023. Compact silicate grains below about half a micrometre in radius are unbound on release, while porous aggregates remain bound only above roughly one and a half micrometres. The method, inputs and limitations are stated in full so that any reader can reproduce or rescale every number from the deposited calculation script. Agreement and disagreement with independent published estimates are reported at their actual size, and the conclusions are limited to what the budget arithmetic supports.