Calculateur d'Échelle des Distances Cosmiques — Formule
## The Cosmic Distance Ladder
Astronomers use overlapping methods to measure distances at different scales:
1. **Radar ranging** (within solar system, < 10 AU)
2. **Stellar parallax** (< 1 000 pc with ground; < 10 000 pc with Gaia)
3. **Spectroscopic parallax / main-sequence fitting** (up to ~10 kpc)
4. **Cepheid variables** (up to ~30 Mpc)
5. **Type Ia supernovae** (up to ~1 000 Mpc)
6. **Hubble's law / redshift** (beyond ~100 Mpc)
Each rung calibrates the next, building confidence across the cosmos.
Astronomers use overlapping methods to measure distances at different scales:
1. **Radar ranging** (within solar system, < 10 AU)
2. **Stellar parallax** (< 1 000 pc with ground; < 10 000 pc with Gaia)
3. **Spectroscopic parallax / main-sequence fitting** (up to ~10 kpc)
4. **Cepheid variables** (up to ~30 Mpc)
5. **Type Ia supernovae** (up to ~1 000 Mpc)
6. **Hubble's law / redshift** (beyond ~100 Mpc)
Each rung calibrates the next, building confidence across the cosmos.
Exemple Résolu
A star cluster at 1000 pc.
- Light-years: 1000 × 3.262 = 3 262 ly
- Parallax: 1/1000 = 0.001 arcsec = 1 mas
- This is within Gaia's reach but beyond ground-based parallax.
- Best methods: space parallax, spectroscopic parallax.