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Plate No. 3,301 — in order of discoveryEntered 2016-08-25

Proxima Cen b

A cold terrestrial world orbiting Proxima Cen, a M5.5 V star, 4.2 ly from Earth. One of 2 charted worlds in its system.

Enter the system →Find it in the night sky →
0.01 AUProxima Cen b
2 worldstemperate zone1s = 1s

Orbit shapes and relative timing are true — worlds sweep faster near their star, as Kepler demands. Spacing is drawn to true scale when the system allows; wide systems open compressed so inner and outer worlds share the page. Dashed orbits are derived from period alone.

The measures

Earth

1.0 R⊕

Proxima Cen b

1.02 R⊕

frozenEarth 255 K · b 218 Kstar-hot

Life outlook

Conceivable

50/ 100
Warmth
64 · weight 40%

~218 K equilibrium vs Earth's 255 K

Size
100 · weight 30%

1.02 R⊕ vs Earth's 1.0 — larger worlds trend gaseous

Star
8 · weight 20%

2900 K dwarf vs the Sun's 5772 K — flares and tidal lock

Orbit
100 · weight 10%

e = 0 vs Earth's 0.017 — swings mean climate whiplash

A strict Earth-similarity index, not a detection: every factor peaks at Earth's own value and they multiply, so one hostile factor sinks the score — only a true Earth twin would reach 100. Equilibrium temperature ignores atmospheres, which can warm a cold world into comfort, or turn a Venus into a furnace.

The world

Class
Terrestrial
Radius
1.02 R⊕
Mass
1.055 M⊕
Density
5.46 g/cm³
Equilibrium temperature
218 K
Starlight received
0.64× Earth

The orbit

Period
11.185 days
Semi-major axis
0.0485 AU
Eccentricity
0

The star

Host
Proxima Cen
Spectral type
M5.5 V
Temperature
2,900 K
Radius
0.14 R☉
Mass
0.12 M☉

The system

Distance
4.2 ly · 1.3 pc
Known planets
2
Stars
3
Coordinates
RA 217.39° · Dec -62.68°

The observation

Star brightness
V 11 · telescope
Atmospheric spectra
none yet
Stellar age
—

The record

Method
Radial Velocity
Facility
European Southern Observatory
Discovery
2016
Parameters published
—
Discovery paperAnglada-Escudé et al. 2016