Stellar Physics Expert

---
name: stellar-physics-expert
version: 1.0.0
description: Expert-level stellar physics covering stellar structure and evolution, nucleosynthesis, stellar atmospheres, variable stars, binary systems, and stellar populations.
author: luo-kai
tags: [stellar physics, stellar evolution, nucleosynthesis, binary stars, stellar atmospheres]
---

# Stellar Physics Expert

## Before Starting
1. Which stellar type or mass range?
2. Structure, evolution, or atmospheres focus?
3. Single or binary star system?

## Core Expertise Areas

### Stellar Structure
Hydrostatic equilibrium: pressure gradient balances gravity at each shell.
Energy transport: radiative diffusion of photons or convective bulk motion.
Mass-luminosity relation: L proportional to M to the power 4 for main sequence.
Lane-Emden equation: polytropic models of stellar structure.
Convection zones: low-mass stars fully convective, solar-type have outer convection zone.

### Stellar Evolution
Pre-main sequence: Hayashi track fully convective, Henyey track radiative.
Zero-age main sequence: star settles into stable hydrogen burning phase.
Red giant: hydrogen shell burning, core contraction, envelope expansion.
Horizontal branch: helium core burning, instability strip contains RR Lyrae.
AGB: asymptotic giant branch, thermal pulses, mass loss, planetary nebula formation.

### Nucleosynthesis
Big Bang nucleosynthesis: H, D, He-3, He-4, Li-7 produced in first minutes.
Stellar nucleosynthesis: CNO cycle, triple-alpha process, s-process.
Explosive nucleosynthesis: r-process in neutron star mergers, p-process in supernovae.
Chemical evolution: enrichment of ISM by stellar winds and supernova ejecta.

### Binary Stars
Classifications: visual, spectroscopic, eclipsing, astrometric binaries.
Roche lobe overflow: mass transfer when star fills its Roche lobe.
Cataclysmic variables: white dwarf accreting from companion, novae and dwarf novae.
Type Ia supernovae: white dwarf reaching Chandrasekhar mass via accretion.

## Best Practices
- Use stellar models appropriate for the mass and metallicity range
- Account for mass loss in evolved star calculations
- Verify spectral type classification with multiple features
- Consider binarity when interpreting unusual stellar properties

## Common Pitfalls
| Pitfall | Fix |
|---|---|
| Ignoring metallicity effects | Metal-poor stars evolve differently from solar |
| Applying solar-calibrated models to all stars | Low-mass and high-mass stars differ significantly |
| Confusing luminosity classes | Use gravity-sensitive lines to distinguish |
| Missing binary contamination in photometry | Check for variability and composite spectra |

## Related Skills
- astrophysics-expert
- physics/nuclear-physics-expert
- physics/quantum-mechanics-expert