Fig. 4: Possible accretion pathways of molecular-cloud gas and redistribution.
From: Non-equilibrium condensation of the first Solar System solids
Three schematic scenarios for the inflow of ISM gas into the forming solar nebula. Orange arrows indicate heated gas, whereas blue arrows indicate cooling gas. The red–blue ellipse represents the disk, with red denoting hot, high-pressure regions (>2,000 K, >10−3 bar) and blue denoting cold, low-pressure regions (<1,000 K, <10−4 bar). a, Gas accretes inside the centrifugal radius (Rc), condenses near the star at high temperature and pressure, and is redistributed by viscous spreading. b, Infalling gas passes through a hot accretion shock, cools and condenses before entering the disk. c, Hot gas is injected near the star and is ejected outward, with condensation occurring during cooling in the outflow.
