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
Could life exist here?
AI analysisProxima Centauri d, discovered in 2025 just 4.24 light-years away, is a rocky world roughly 70 percent of Earth's radius with an equilibrium temperature of 282 Kelvin—a cool 9 degrees Celsius, comparable to Earth's coldest regions. Its 5.12-day orbit around the dim M-dwarf Proxima Centauri places it closer to its star than Mercury is to our Sun, yet the star's feeble output keeps the planet temperate rather than scorched. The planet's circular orbit and modest density of 4.31 grams per cubic centimeter suggest a solid, likely silicate-rich body rather than a volatile-rich or icy one. However, its proximity to a magnetically active red dwarf raises serious questions about atmospheric retention and stellar radiation over geological timescales. The habitability score of 82 reflects genuine potential, but liquid water and a breathable atmosphere remain entirely unconfirmed. What makes Proxima d exceptional is its sheer proximity and the radial velocity method's rare success at detecting such a small, slow-orbiting world—making it an unprecedented nearby laboratory for understanding how rocky planets form around the galaxy's most common stars.
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.