Gas and radiation pressure in stellar matter
In a nondegenerate ideal ionized mixture in local thermal equilibrium, ions and electrons contribute their number densities to gas pressure; isotropic thermal radiation adds a radiation-pressure term.
Key knowledge
In a nondegenerate ideal ionized mixture in local thermal equilibrium, ions and electrons contribute their number densities to gas pressure; isotropic thermal radiation adds a radiation-pressure term. P=(nᵢ+nₑ)k_BT+a_RT⁴/3. Ionization and composition determine particle numbers; different electron and ion mean masses must not be conflated.
Values and equations
P=(nᵢ+nₑ)k_BT+a_RT⁴/3; a_R=4σ_SB/c
- P
- total gas plus radiation pressure Pa
- nᵢ,nₑ
- ion and free-electron number densities m⁻³
- k_B
- Boltzmann constant J K⁻¹
- T
- local temperature K
- a_R
- radiation energy-density constant J m⁻³ K⁻⁴
- σ_SB
- Stefan–Boltzmann constant W m⁻² K⁻⁴
- c
- vacuum light speed m s⁻¹
Conditions and scope
- Common local temperature; negligible nonideal interactions and degeneracy for the gas terms; isotropic equilibrium photons for the radiation term.
- Degenerate electrons, partial ionization, Coulomb effects, anisotropic radiation and magnetic stresses require an adapted equation of state.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read separate ideal-ion/electron pressure and radiation terms. Excluded the notes' misleading repulsion-only account of ideal gas pressure and ambiguous mean-mass conventions.
2026-10-10 · Independent AI editorial review: All44 exact root-authored compact records, equations/variable units/conditions and140 origin edges accepted after independently reading final6/18 with bounded primary bodies and matching prior38/122 scientific fingerprints unchanged. Exact claim/edge review is distinct from combined inventory scope and separate CLE26 approval; no entire cited books or old-corpus experimental revalidation is asserted. Receipt: cosmos-completion-independent-content-and-inventory-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- uni-cosmos-gas-radiation-eos
- Revision
- core.1
- Structured reference record
- University core expansion