Proxima Cen d
Proxima Cen d is a terrestrial planet orbiting the M5.5 V star Proxima Cen in the constellation Centaurus. It lies about 4 light-years from Earth and was discovered in 2025 using the radial velocity method.
Is Proxima Cen d in the Habitable Zone?
Proxima Cen d orbits inside the inner edge of the habitable zone of Proxima Cen. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Proxima Cen: 0.032–0.085 AU (conservative: 0.041–0.081 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on Proxima Cen d
The equilibrium temperature of Proxima Cen d is about 282 K (9 °C) — in a range broadly comparable to Earth, whose equilibrium temperature is 255 K. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 1.81 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Proxima Cen d — one full orbit around Proxima Cen — lasts 5.12 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.029 AU — closer to its star than Mercury is to the Sun.
How Was Proxima Cen d Discovered?
Proxima Cen d was discovered in 2025 using the radial velocity method, with observations from La Silla Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is Proxima Cen d?
Proxima Cen d is 4.2 light-years (1.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 2022. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 73,920 years to make the journey.
The Host Star: Proxima Cen
Proxima Cen d belongs to a system of 3 stars; it orbits Proxima Cen.
Proxima Cen
- Spectral type
- M5.5 V
- Surface temperature
- 2,900 K (Sun: 5,772 K)
- Mass
- 0.12 M☉
- Radius
- 0.14 R☉
- Luminosity
- 0.0015 L☉
The Proxima Cen Planetary System
Proxima Cen d is one of 2 known planets in the Proxima Cen system. Its siblings:
- Proxima Cen b (Terrestrial)
Proxima Cen d — Complete Data
| Mass (best estimate) | 0.26 Earth masses |
|---|---|
| Orbital period | 5.12 days |
| Orbital distance | 0.029 AU |
| Equilibrium temperature | 282 K (9 °C) |
| Stellar irradiation | 1.81× Earth |
| Distance from Earth | 4.2 light-years (1.3 parsecs) |
| Constellation | Centaurus |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-07-29. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Proxima Cen d
Is Proxima Cen d habitable?
No — Proxima Cen d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Proxima Cen d?
Proxima Cen d is about 4 light-years from Earth in the constellation Centaurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 73,920 years to get there.
How long is a year on Proxima Cen d?
One orbit around Proxima Cen takes 5.1 Earth days — short enough that 71 of its years would fit into one Earth year.
Explore Proxima Cen d in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
