Key parameters at a glance

A radius of 0.69 Earth radii
A mass of 0.26 Earth masses
Surface gravity around 0.54 g
An orbital period of 5.123 days
Semi-major axis 0.0288 AU
Equilibrium temperature 282 K (9 °C)
Distance from Earth 4.24 light-years
Earth Similarity Index 0.881
Travel time at Voyager 1 speed 74,841 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

Proxima Centauri d is a confirmed exoplanet orbiting the red dwarf star Proxima Centauri, the closest star to the Sun and part of the Alpha Centauri triple star system. Together with one or two other planets in the Proxima Centauri system, it is the closest known exoplanet to the Solar System, located approximately 4.2 light-years away in the constellation of Centaurus. The first signs of the exoplanet emerged as a weak 5.15-day signal in radial velocity data taken from the Very Large Telescope during a 2020 study on Proxima b's mass. This signal was formally proposed to be a candidate exoplanet by Faria et al. in a follow-up paper published in February 2022, and was independently confirmed in 2025.

Excerpted from Wikipedia · full article

1 sibling around Proxima Cen

Proxima Cen d shares its host star with 1 other confirmed planet. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
Proxima Cen d this	Rocky Terrestrial	0.69	0.26	5.123	282	2025
Proxima Cen b	Rocky Terrestrial	1.02	1.06	11.185	218	2016

Proxima Cen d Planet Profile

Physical Specs

Radius

0.69 R⊕

Radius (Jupiter)

0.062 R♃

Mass

0.26 M⊕

Mass (Jupiter)

0.001 M♃

Density

4.31 g/cm³

Surface Gravity

0.54 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.881

HZ Position Inner

Controversial No

Discovery

Year 2025

Method Radial Velocity

Facility La Silla Observatory

Telescope 3.6 m ESO Telescope

Size rank in cohort

Rank by radius

#531of 570

top 93.0%

This planet

0.69R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

EPIC 201497682 b 0.69 R⊕ Kepler-141 b 0.69 R⊕ K2-116 b 0.69 R⊕

Metric	Earth	Proxima Cen d	Jupiter
Radius (R⊕)	1.00	0.69	11.21
Mass (M⊕)	1.00	0.26	317.83
Density (g/cm³)	5.51	4.31	1.33
Surface Gravity (g)	1.00	0.54	2.53
Insolation (S⊕)	1.00	1.81	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	0.260 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HIP

HIP 70890

TIC

TIC 388857263

Gaia DR2

Gaia DR2 5853498713160606720

Gaia DR3

Gaia DR3 5853498713190525696

System

alf Cen

Percentile among Rocky Terrestrial cohort

Radius 0.692 R⊕ · percentile 7 / cohort 570

Mass 0.260 M⊕ · percentile 5 / cohort 570

Orbital period 5.12 d · percentile 55 / cohort 567

Distance 1.30 pc · percentile 0 / cohort 566

ESI 0.881 · percentile 90 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

5.123 days

Semi-major axis

0.0288 AU

Eccentricity

0.000

Inclination

— °

Year Length

A year here lasts approximately 5.12 Earth days (1.4% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0288 AU.

Eq. Temperature

282K

(9 °C)

Insolation (S⊕)

1.81

Earth = 1.00

Earth Similarity (ESI)

0.881

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — liquid water is physically possible with adequate atmospheric pressure. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Su & Aacute Rez Mascare & Ntilde O et al. 2025

Instrument

NIRPS Spectrograph

Publication

2025-08

Observation locale

Ground

Discovery cohort

Planets confirmed in 2025 at La Silla Observatory (12 shown).

TOI-1203 c · Sub-Neptune HD 23079 c · Sub-Neptune HD 196067 c · Sub-Neptune HD 87816 b · Gas Giant HD 102888 b · Gas Giant HD 94890 c · Gas Giant TOI-756 c · Gas Giant TOI-1203 e · Neptune-like HD 94890 b · Gas Giant HD 87816 c · Gas Giant GJ 2126 b · Gas Giant HD 28471 d · Sub-Neptune

Host System: Proxima Cen

Spectral Class

M-type red dwarf

Effective Temperature

2,900 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.141 R☉

Stellar Mass

0.122 M☉

Metallicity [Fe/H]

—

Extended Stellar Properties

Surface gravity (log g)

5.164 dex

Stellar density

48.763 g/cm³

Rotation period

83.20 days

Distance

1.30 parsec

Light-years 4.24 ly

V-band magnitude

11.01 mag

Voyager-speed travel 74,841 yr

Multi-band Host Photometry — 8 bands

Astrometric Data

Parallax

768.500 mas

Total Proper Motion

3,858.866 mas/yr

PM Right Ascension

-3,781.31 mas/yr

PM Declination

769.77 mas/yr

Galactic Cartesian (pc)

x = -0.365 · y = -0.279 · z = -0.888

Equatorial (J2000)

RA 217.39347° · Dec -62.67618°

Galactic ℓ, b

313.926° · -1.918°

Ecliptic λ, β

239.088° · -44.768°

HTM-20 index

-410784514

Observation Record

Photometric series

RV measurements

Archive notes

Wikipedia → Image: Wikimedia Commons · ESO/L. Calçada · CC BY 4.0