Exoplanets Expert

---
name: exoplanets-expert
version: 1.0.0
description: Expert-level exoplanet science covering detection methods, orbital dynamics, planetary atmospheres, habitability, and the search for biosignatures.
author: luo-kai
tags: [exoplanets, transits, radial velocity, atmospheres, habitability, biosignatures]
---

# Exoplanets Expert

## Before Starting
1. Detection, characterization, or habitability focus?
2. Which detection method?
3. Small rocky planets or giant planets?

## Core Expertise Areas

### Detection Methods
Transit: planet crosses star, flux decreases by Rp squared over Rs squared, period from timing.
Radial velocity: Doppler shift of stellar lines, measures m sin i.
Direct imaging: high contrast, wide-separation planets, young or massive targets.
Microlensing: brightening when planet-star system passes near background star.
Astrometry: stellar wobble in position, Gaia promising for long-period planets.

### Atmospheric Characterization
Transmission spectroscopy: during transit, starlight through atmosphere reveals absorption features.
Emission spectroscopy: secondary eclipse, thermal emission from planet measured directly.
Phase curves: full orbit photometry, day-night temperature contrast.
JWST: revolutionary sensitivity for small planet atmospheres, TRAPPIST-1 prime targets.

### Planetary Populations
Fulton gap: bimodal radius distribution at 1.5 to 2 Earth radii from photoevaporation.
Hot Jupiters: close-in giant planets, migrated from outer disk.
Super-Earths: 1 to 4 Earth radii, most common type found by Kepler.
Occurrence rates: Kepler statistics, eta-Earth for solar-type stars.

### Habitability
Habitable zone: range of orbital distances for surface liquid water.
M dwarf habitability: tidal locking, stellar flares, atmospheric erosion concerns.
Biosignatures: O2 plus CH4 disequilibrium, O3 UV shield, N2O from biology.
False positives: abiotic O2 from photolysis of CO2, careful context needed.

## Best Practices
- Combine multiple detection methods for complete planet characterization
- Account for detection biases when inferring occurrence rates
- Consider host star properties when assessing habitability
- Validate atmospheric detections against multiple spectral features

## Common Pitfalls
| Pitfall | Fix |
|---|---|
| Confusing equilibrium temperature with surface temperature | Greenhouse effect raises surface temperature significantly |
| Single biosignature as detection | Multiple independent lines of evidence needed |
| Ignoring stellar variability in transit analysis | Starspots can mimic or mask transit signals |
| Earth-centric habitability only | Other types of planets may support life |

## Related Skills
- planetary-science-expert
- astrophysics-expert
- cosmology-expert