Key parameters at a glance

A radius of 1.02 Earth radii
A mass of 1.06 Earth masses
Surface gravity around 1.01 g
An orbital period of 11.185 days
Semi-major axis 0.0485 AU
Equilibrium temperature 218 K (-55 °C)
Distance from Earth 4.24 light-years
Earth Similarity Index 0.809
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 b is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri in the constellation Centaurus. It can also be referred to as Proxima b, or Alpha Centauri Cb. The host star is the closest star to the Sun, at a distance of about 4.2 light-years from Earth, and is part of the larger triple star system Alpha Centauri. Proxima b and Proxima d, along with the currently disputed Proxima c, are the closest known exoplanets to the Solar System.

Excerpted from Wikipedia · full article

1 sibling around Proxima Cen

Proxima Cen b 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	Rocky Terrestrial	0.69	0.26	5.123	282	2025
Proxima Cen b this	Rocky Terrestrial	1.02	1.06	11.185	218	2016

Proxima Cen b Planet Profile

Physical Specs

Radius

1.02 R⊕

Radius (Jupiter)

0.091 R♃

Mass

1.06 M⊕

Mass (Jupiter)

0.003 M♃

Density

5.46 g/cm³

Surface Gravity

1.01 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.809

HZ Position Habitable

Controversial No

Discovery

Year 2016

Method Radial Velocity

Facility European Southern Observatory

Telescope Multiple Telescopes

Size rank in cohort

Rank by radius

#311of 570

top 54.4%

This planet

1.02R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-336 b 1.02 R⊕ Kepler-130 b 1.02 R⊕ Kepler-192 d 1.02 R⊕

Metric	Earth	Proxima Cen b	Jupiter
Radius (R⊕)	1.00	1.02	11.21
Mass (M⊕)	1.00	1.06	317.83
Density (g/cm³)	5.51	5.46	1.33
Surface Gravity (g)	1.00	1.01	2.53
Insolation (S⊕)	1.00	0.64	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	1.055 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 1.020 R⊕ · percentile 44 / cohort 570

Mass 1.055 M⊕ · percentile 41 / cohort 570

Orbital period 11.18 d · percentile 81 / cohort 567

Distance 1.30 pc · percentile 0 / cohort 566

ESI 0.809 · percentile 88 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

11.185 days

Semi-major axis

0.0485 AU

Eccentricity

0.000

Inclination

— °

Year Length

A year here lasts approximately 11.18 Earth days (3.1% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0485 AU.

Extended Orbital Architecture

RV semi-amplitude (K)

1.226 m/s

Transit mid-time (BJD)

2,457,897.9000

Long. of periastron (ω)

3.30°

Angular separation (arcsec)

37.30000

Eq. Temperature

218K

(-55 °C)

Insolation (S⊕)

0.64

Earth = 1.00

Earth Similarity (ESI)

0.809

0 = alien, 1 = Earth-identical

Within the conservative habitable zone — surface water would be frozen. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Anglada Escud Eacute et al. 2016

Instrument

Multiple Instruments

Publication

2016-08

Observation locale

Ground

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/M. Kornmesser · CC BY 4.0