Key parameters at a glance

A radius of 0.72 Earth radii
A mass of 0.30 Earth masses
Surface gravity around 0.58 g
An orbital period of 3.154 days
Semi-major axis 0.0229 AU
Equilibrium temperature 438 K (165 °C)
Distance from Earth 5.96 light-years
Earth Similarity Index 0.655
Travel time at Voyager 1 speed 105,059 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

Barnard's Star b, or Barnard b, is a sub-Earth-mass exoplanet closely orbiting Barnard's Star, a nearby red dwarf star six light-years from Earth. The planet was discovered using radial velocity observations from the ESPRESSO spectrograph on the Very Large Telescope, and was announced on 1 October 2024. It is the second from its star of four known planets in its system.

Excerpted from Wikipedia · full article

3 siblings around Barnard's star

Barnard b shares its host star with 3 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
Barnard d	Rocky Terrestrial	0.69	0.26	2.340	483	2025
Barnard b this	Rocky Terrestrial	0.72	0.30	3.154	438	2024
Barnard c	Rocky Terrestrial	0.74	0.34	4.124	400	2025
Barnard e	Rocky Terrestrial	0.64	0.19	6.739	340	2025

Barnard b Planet Profile

Physical Specs

Radius

0.72 R⊕

Radius (Jupiter)

0.064 R♃

Mass

0.30 M⊕

Mass (Jupiter)

0.001 M♃

Density

4.40 g/cm³

Surface Gravity

0.58 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.655

HZ Position Inner

Controversial No

Discovery

Year 2024

Method Radial Velocity

Facility Paranal Observatory

Telescope 8.2 m ESO VLT UT3 Melipal Telescope

Size rank in cohort

Rank by radius

#522of 570

top 91.4%

This planet

0.72R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-1559 b 0.72 R⊕ Kepler-1850 b 0.73 R⊕ Kepler-1339 b 0.71 R⊕

Metric	Earth	Barnard b	Jupiter
Radius (R⊕)	1.00	0.72	11.21
Mass (M⊕)	1.00	0.30	317.83
Density (g/cm³)	5.51	4.40	1.33
Surface Gravity (g)	1.00	0.58	2.53
Insolation (S⊕)	1.00	6.76	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	0.299 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HIP

HIP 87937

TIC

TIC 325554331

Gaia DR2

Gaia DR2 4472832130942575872

Gaia DR3

Gaia DR3 4472832130942575872

System

Barnard's star

Percentile among Rocky Terrestrial cohort

Radius 0.720 R⊕ · percentile 8 / cohort 570

Mass 0.299 M⊕ · percentile 6 / cohort 570

Orbital period 3.15 d · percentile 35 / cohort 567

Distance 1.83 pc · percentile 0 / cohort 566

ESI 0.655 · percentile 80 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

3.154 days

Semi-major axis

0.0229 AU

Eccentricity

0.030

Inclination

— °

Year Length

A year here lasts approximately 3.15 Earth days (0.9% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0229 AU.

Extended Orbital Architecture

RV semi-amplitude (K)

0.440 m/s

Transit mid-time (BJD)

2,460,139.2040

Long. of periastron (ω)

3.80°

Angular separation (arcsec)

12.50000

Eq. Temperature

438K

(165 °C)

Insolation (S⊕)

6.76

Earth = 1.00

Earth Similarity (ESI)

0.655

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Gonzalez Hernandez et al. 2024

Instrument

ESPRESSO

Publication

2024-10

Observation locale

Ground

Host System: Barnard's star

Spectral Class

M-type red dwarf

Effective Temperature

3,195 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.185 R☉

Stellar Mass

0.162 M☉

Metallicity [Fe/H]

-0.56

Extended Stellar Properties

Surface gravity (log g)

4.900 dex

Stellar density

31.638 g/cm³

Systemic radial velocity

-110.50 km/s

Rotation period

142.00 days

Activity index (log R'HK)

-5.800

Metallicity ratio

[Fe/H]

Distance

1.83 parsec

Light-years 5.96 ly

V-band magnitude

9.54 mag

Voyager-speed travel 105,059 yr

Multi-band Host Photometry — 13 bands

Astrometric Data

Parallax

547.451 mas

Total Proper Motion

10,393.551 mas/yr

PM Right Ascension

-802.80 mas/yr

PM Declination

10,362.50 mas/yr

Galactic Cartesian (pc)

x = -0.010 · y = -0.997 · z = 0.083

Equatorial (J2000)

RA 269.44861° · Dec 4.73798°

Galactic ℓ, b

31.048° · 14.086°

Ecliptic λ, β

269.373° · 28.176°

HTM-20 index

1313887056

Observation Record

Photometric series

Stellar spectra

Archive notes

Wikipedia → Image: Wikimedia Commons · ESO/M. Kornmesser · CC BY 4.0