Proxima Cen b
Rank #1 of the ranked catalogue · Discovered by Radial Velocity in 2016
0.876
Earth-2.0 index
rank #1
0.915
Earth Similarity Index
0.897–0.932 (68% CI)
100%
Conservative HZ probability
1.02 R⊕
Radius
mass: msini_lower_limit
At a glance
Proxima Cen lies 4.24 light-years (1.301 pc) from the Sun. Proxima Cen is a M5.5 V star with 0.122× the Sun's mass and 0.141× its radius (effective temperature 2900 K, versus the Sun's 5772 K). It is one of 3 stars in this system hosting 2 known planets. Proxima Cen b is 1.02× Earth's radius, at least 1.05× Earth's mass (a radial-velocity minimum mass, not the true mass), completing one orbit every 11.2 days at 0.0485 AU. It receives about 0.64× the flux Earth gets from the Sun, for an equilibrium temperature near 227 K (Earth's is 254 K).
Orbit and habitable-zone boundaries computed in Python from this system’s actual parameters. Sizes and the overall scale are compressed for visibility, not literal; green = conservative HZ, gold = optimistic HZ.
| Boundary | S_eff (Earth units) |
|---|---|
| recent venus | 1.4918 |
| runaway greenhouse | 0.8629 |
| moist greenhouse | 0.8521 |
| maximum greenhouse | 0.2291 |
| early mars | 0.2020 |
No published transmission spectrum exists for this planet in the NASA Exoplanet Archive.
Planet is not flagged as transiting; a light curve cannot show a transit.
| Parameter | Value | Source |
|---|---|---|
| Planet radius | 1.0200 | archive-calculated (not a publication) |
| Planet mass | 1.0550 | Suárez Mascareño et al. 2025 |
| Orbital period | 11.1846 | Suárez Mascareño et al. 2025 |
| Semi-major axis | 0.0485 | Suárez Mascareño et al. 2025 |
| Incident flux | 0.6410 | Suárez Mascareño et al. 2025 |
| Equilibrium temperature | 218.0000 | Suárez Mascareño et al. 2025 |
| Bulk density | 5.4600 | archive-calculated (not a publication) |
| Orbital eccentricity | 0.0000 | Suárez Mascareño et al. 2025 |
| Stellar effective temperature | 2900.0000 | Suárez Mascareño et al. 2025 |
| Stellar radius | 0.1410 | Suárez Mascareño et al. 2025 |
| Stellar mass | 0.1221 | Suárez Mascareño et al. 2025 |
| Stellar luminosity | -2.8210 | Suárez Mascareño et al. 2025 |
| System distance | 1.3012 | TICv8 |
Component scores
Earth similarity
0.915Conservative habitability
0.946Observational confidence
0.730Characterisation potential
—Evidence
- Independent references
- 5
- Published parameter sets
- 5
- Composite parameter sources
- 3 · mixed
- Default-solution coverage
- 83%
- Composite ↔ default difference
- 0% median
- Uncertainty coverage
- 83%
- Discovery method
- Radial Velocity
- Discovery year
- 2016
The archive composite selects values from multiple publications. This is disclosed separately and is not automatically penalised.
Observability
- TSM
- n/a (non-transiting)
- RV semi-amplitude (expected)
- 1.226 m/s
- Transit-time σ at 2030
- —
- Max angular separation
- 37.26 mas
- Reflected-light contrast
- 7.68e-8
Follow-up lanes are diagnostics, not ranking inputs. Reflected light assumes Ag = 0.30 and Lambertian quadrature.
Identifiers
- system_name
- alf Cen
Other planets in this system
- Proxima Cen d5.12 d
Any rendering of this world is a scientifically informed visualisation, not an image. No exoplanet has been imaged at surface resolution. Surface and cloud appearance are illustrative of a physically plausible class, not observations.