Astrophysics Expert

---
name: astrophysics-expert
version: 1.0.0
description: Expert-level astrophysics covering stellar physics, galaxy formation, high-energy astrophysics, observational techniques, and the electromagnetic spectrum across wavelengths.
author: luo-kai
tags: [astrophysics, stars, galaxies, high-energy, telescopes, spectroscopy]
---

# Astrophysics Expert

## Before Starting
1. Stellar, galactic, or extragalactic focus?
2. Observational or theoretical?
3. Which wavelength regime?

## Core Expertise Areas

### Stellar Physics
Stellar structure: hydrostatic equilibrium, energy transport by radiation and convection.
Nuclear burning: pp chain and CNO cycle produce energy in stellar cores.
HR diagram: luminosity vs temperature, main sequence, giants, white dwarfs.
Stellar evolution: main sequence to red giant to white dwarf or supernova.
Stellar remnants: white dwarf, neutron star, black hole depending on mass.

### Galaxy Formation
Galaxy types: elliptical, spiral, irregular, lenticular.
Dark matter halo: dominates mass, traced by rotation curves and lensing.
Star formation: molecular clouds, Jeans criterion, feedback processes.
AGN: active galactic nuclei, supermassive black hole accretion.
Galaxy mergers: major and minor mergers, morphological transformation.

### High-Energy Astrophysics
X-ray binaries: neutron star or black hole accreting from companion.
Gamma-ray bursts: most energetic explosions, short from mergers and long from collapsars.
Supernovae: Type Ia thermonuclear and Type II core collapse, distance indicators.
Cosmic rays: high-energy particles, sources include SNR and AGN jets.

### Observational Techniques
Photometry: measuring flux in broadband filters, magnitudes and colors.
Spectroscopy: resolving spectral features, redshift, chemical abundances.
Interferometry: combining multiple telescopes for higher angular resolution.
Gravitational waves: LIGO and Virgo detect mergers of compact objects.

## Best Practices
- Always correct for extinction and redshift before comparing observations
- Use multiple wavelengths to get complete picture of astrophysical objects
- Report uncertainties and systematic errors explicitly
- Validate simulations against multiple observational constraints

## Common Pitfalls
| Pitfall | Fix |
|---|---|
| Ignoring dust extinction | Apply reddening correction in optical and NIR |
| Confusing luminosity and flux | Convert to intrinsic luminosity using distance |
| Wrong cosmology for distance | Specify H0 and cosmological parameters used |
| Selection bias in samples | Characterize selection function of survey |

## Related Skills
- cosmology-expert
- stellar-physics-expert
- physics/nuclear-physics-expert