Key parameters at a glance

A radius of 2.05 Earth radii
A mass of 4.55 Earth masses
Surface gravity around 1.09 g
An orbital period of 6.226 days
Semi-major axis 0.0539 AU
Equilibrium temperature 559 K (286 °C)
Distance from Earth 116.41 light-years
Earth Similarity Index 0.479
Travel time at Voyager 1 speed 2,052,901 years
Almost certainly tidally locked to its host star given the close orbit

3 siblings around LHS 1903

LHS 1903 c 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
LHS 1903 b	Super-Earth	1.38	3.28	2.156	796	2026
LHS 1903 c this	Sub-Neptune	2.05	4.55	6.226	559	2026
LHS 1903 d	Sub-Neptune	2.50	5.96	12.566	442	2026
LHS 1903 e	Super-Earth	1.73	5.79	29.318	333	2026

LHS 1903 c Planet Profile

Physical Specs

Radius

2.05 R⊕

Radius (Jupiter)

0.183 R♃

Mass

4.55 M⊕

Mass (Jupiter)

0.014 M♃

Density

2.91 g/cm³

Surface Gravity

1.09 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.479

HZ Position Inner

Controversial No

Discovery

Year 2026

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#1902of 1978

top 96.1%

This planet

2.05R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

TOI-776 c 2.05 R⊕ TOI-712 b 2.05 R⊕ Wolf 503 b 2.04 R⊕

Metric	Earth	LHS 1903 c	Jupiter
Radius (R⊕)	1.00	2.05	11.21
Mass (M⊕)	1.00	4.55	317.83
Density (g/cm³)	5.51	2.91	1.33
Surface Gravity (g)	1.00	1.09	2.53
Insolation (S⊕)	1.00	16.20	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	4.550 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HIP

HIP 34730

TIC

TIC 318022259

Gaia DR2

Gaia DR2 978086481343568128

Gaia DR3

Gaia DR3 978086481343568128

System

LHS 1903

Percentile among Sub-Neptune cohort

Radius 2.046 R⊕ · percentile 4 / cohort 1978

Mass 4.550 M⊕ · percentile 2 / cohort 1978

Orbital period 6.23 d · percentile 18 / cohort 1946

Distance 35.69 pc · percentile 9 / cohort 1975

ESI 0.479 · percentile 68 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

6.226 days

Semi-major axis

0.0539 AU

Eccentricity

0.089

Inclination

— °

Year Length

A year here lasts approximately 6.23 Earth days (1.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0539 AU.

Transit Fingerprint

Depth

0.121 %

Duration

1.986 h

Impact parameter b

0.513

Rp / R★

0.034790

Transit midpoint (BJD)

2,458,844.3692

Photometric dip

Transit produces a flux drop of 1,210 ppm lasting ≈ 1.99 h.

Extended Orbital Architecture

Planet / star radius ratio

0.034790

Semi-major axis / stellar radius

21.480

Impact parameter (b)

0.513

RV semi-amplitude (K)

2.400 m/s

Transit mid-time (BJD)

2,458,844.3692

Long. of periastron (ω)

288.00°

Angular separation (arcsec)

1.51000

Eq. Temperature

559K

(286 °C)

Insolation (S⊕)

16.20

Earth = 1.00

Earth Similarity (ESI)

0.479

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.

Detection Signatures

Transit photometry

A transit dip has been observed from at least one telescope.

Radial velocity

Stellar wobble has been measured spectroscopically.

Discovery Paper

Primary reference

Wilson et al. 2026

Instrument

TESS CCD Array

Publication

2026-02

Observation locale

Space

Discovery cohort

Planets confirmed in 2026 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-2094 b · Super-Earth TOI-6716 b · Rocky Terrestrial TOI-1080 b · Rocky Terrestrial TOI-1243 b · Sub-Neptune TOI-4529 b · Super-Earth TOI-7384 b · Sub-Neptune LHS 1903 d · Sub-Neptune TOI-5734 b · Sub-Neptune TOI-5788 c · Sub-Neptune LHS 1903 b · Super-Earth TOI-5788 b · Super-Earth TOI-1232 c · Neptune-like

Host System: LHS 1903

Spectral Class

M-type red dwarf

Effective Temperature

3,664 K — cooler than the Sun (5,778 K)

Estimated Age

7.08 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.539 R☉

Stellar Mass

0.538 M☉

Metallicity [Fe/H]

-0.11

Extended Stellar Properties

Surface gravity (log g)

4.750 dex

Stellar density

5.343 g/cm³

Rotation period

40.80 days

Metallicity ratio

[Fe/H]

Distance

35.69 parsec

Light-years 116.41 ly

V-band magnitude

12.23 mag

Voyager-speed travel 2,052,901 yr

Multi-band Host Photometry — 7 bands

Astrometric Data

Parallax

27.989 mas

Total Proper Motion

578.094 mas/yr

PM Right Ascension

-93.08 mas/yr

PM Declination

-570.55 mas/yr

Galactic Cartesian (pc)

x = -0.204 · y = 0.633 · z = 0.747

Equatorial (J2000)

RA 107.86583° · Dec 48.32793°

Galactic ℓ, b

168.989° · 23.094°

Ecliptic λ, β

103.079° · 25.697°

HTM-20 index

-778388913