Host star — Proxima Cen
- Spectral type
- M5.5 V
- Temperature
- 2,900 K
- Radius
- 0.14 R☉
- Mass
- 0.12 M☉
- Luminosity
- 0.002 L☉
- Distance
- 1.3 pc (4.2 ly)
Red dwarf — the most common type of star. Cool and small.
Very cool — a faint red dwarf.
Proxima Cen d
Orbits Proxima Cen · 4.2 light-years from Earth
RockyRadial Velocity2025ESI 82 · Very Earth-like
Radius
0.69×
Earth
Mass
0.3×
Earth
Year
5d
Temp
282 K
9°C
Gravity
0.5×
Earth
Distance
4.2
ly
What it would be like
Proxima Cen d is a rocky world, potentially similar in composition to Earth or Mars — a solid surface you could, in theory, stand on.
Surface gravity is about 0.5g — noticeably lighter what you're used to on Earth.
With an equilibrium temperature around 9°C, this planet sits in the temperature range where liquid water could potentially exist on the surface — a key ingredient for life as we know it.
A year here is only 5.1 Earth days. Seasons, if they exist, change in a matter of hours.
Earth comparison
Logarithmic bars so Jupiter-class planets fit the same scale as Earth-size worlds.
Radius0.69R⊕
1/25×Earth = 125×
Mass0.26M⊕
1/10000×Earth = 110000×
Surface gravity0.54g
1/100×Earth = 1100×
Equilibrium temp282 K(9°C)
0 KEarth 255 K2500 K
Side-by-side with Earth
Temperature in context
Liquid N₂Mars avgEarth eq.Earth sfc.Boiling H₂OVenus
Discovery & orbit
- Method
- Radial Velocity
- Year
- 2025
- Facility
- La Silla Observatory
- Semi-major axis
- 0.0288 AU
- Period
- 5.12 days
- Eccentricity
- 0.0000
- Density
- 4.31 g/cm³
Detected by the star's wobble — gravitational tug from the orbiting planet shifts spectral lines.
Nearly circular orbit.
Rocky composition likely. Earth is 5.51 g/cm³.
Discovered via · Radial velocity
The star's wobble — gravitational tug from the planet shifts its spectrum
A planet orbiting a star pulls it slightly back and forth. That motion compresses the star's light when moving toward us (blueshift) and stretches it away (redshift). Precision spectrographs detect the wobble at metres-per-second — enough to infer a planet's mass and orbit.
- Overall share
- ~19% of discoveries
- Best for
- Massive, close-in planets around nearby bright stars
Orbital Animation
Proxima CenProxima Cen dOrbitHabitable zone
Drag to rotate · scroll to zoomSemi-major axis: 0.029 AUEccentricity: 0.0000Period: 5.1 days
Hertzsprung–Russell Diagram
Where this host star sits among … exoplanet host stars. The main sequence band runs diagonally — giants and supergiants sit above, white dwarfs below.
OBAFGKMCurrent star
How far is 4.2 light-years?
- A light beam leaving Earth right now would arrive in 4.2 years.
- At Voyager 1's speed (17 km/s), the trip would take approximately 74,843 years.
- A radio signal sent today would arrive in 4.2 years — and the reply wouldn't come back for twice that.
Earth Similarity Index
82/1000 — Nothing like Earth100 — Identical to Earth
ESI combines radius similarity and equilibrium temperature similarity. Earth = 100. Mars ≈ 73. Venus ≈ 44. This score reflects two physical parameters only — not atmosphere, water, or magnetic field.