Radiative heating of interstellar grains falling toward the solar nebula: 1-D diffusion calculations.

Area of Science:

• Planetary Science
• Astrophysics
• Astrochemistry

Background:

• The early Solar System formed from a collapsing molecular cloud containing interstellar grains.
• Infalling grains were primarily heated by the protosun's radiation before reaching the solar nebula accretion disk.
• Understanding grain survival is crucial for studying interstellar inheritance in the Solar System.

Purpose of the Study:

• To estimate the temperatures experienced by infalling interstellar grains.
• To determine which grain species could survive the protosun's radiation field.
• To investigate the influence of accretion and rotation rates on grain survival.

Main Methods:

• Conducted 1D radiative diffusion calculations using 2D, cylindrically symmetric models of cloud collapse.
• Incorporated recent models for interstellar grain composition and radiative properties.
• Analyzed the impact of varying accretion and molecular cloud rotation rates.

Main Results:

• High accretion rates or low rotation rates led to the vaporization of all infalling grains, including silicates and iron.
• Low accretion rates or high rotation rates allowed non-ice species, including volatile organics, to survive intact.
• Grain survival is highly sensitive to accretion and rotation parameters, with a wide range of possible outcomes.

Conclusions:

• The survival of interstellar grains in the early Solar System was dependent on dynamic conditions like accretion and rotation rates.
• Results provide input for models of grain processing at the solar nebula's accretion shock and interstellar inheritance.
• Partial survival of organic grains suggests intact material entered the disk at distances greater than a few AU.