Key parameters at a glance

A radius of 2.20 Earth radii
A mass of 5.46 Earth masses
Surface gravity around 1.13 g
An orbital period of 13.077 days
Distance from Earth 211.98 light-years
Earth Similarity Index 0.750
Travel time at Voyager 1 speed 3,738,317 years

3 siblings around TOI-1203

TOI-1203 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
TOI-1203 b	Super-Earth	1.52	3.51	4.157	1,361	2025
TOI-1203 c this	Sub-Neptune	2.20	5.46	13.077	—	2025
TOI-1203.01	Sub-Neptune	2.92	7.39	25.503	744	2021
TOI-1203 e	Neptune-like	7.31	42.10	204.590	—	2025

TOI-1203 c Planet Profile

Physical Specs

Radius

2.20 R⊕

Radius (Jupiter)

0.196 R♃

Mass

5.46 M⊕

Mass (Jupiter)

0.017 M♃

Density

2.82 g/cm³

Surface Gravity

1.13 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.750

HZ Position Unknown

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

#1673of 1978

top 84.5%

This planet

2.20R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

HD 110067 b 2.20 R⊕ Kepler-169 e 2.20 R⊕ Kepler-122 d 2.20 R⊕

Metric	Earth	TOI-1203 c	Jupiter
Radius (R⊕)	1.00	2.20	11.21
Mass (M⊕)	1.00	5.46	317.83
Density (g/cm³)	5.51	2.82	1.33
Surface Gravity (g)	1.00	1.13	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	5.460 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HIP

HIP 54779

TIC

TIC 23434737

Gaia DR2

Gaia DR2 5402390257832925952

Gaia DR3

Gaia DR3 5402390257832925952

System

TOI-1203

Percentile among Sub-Neptune cohort

Radius 2.200 R⊕ · percentile 15 / cohort 1978

Mass 5.460 M⊕ · percentile 15 / cohort 1978

Orbital period 13.08 d · percentile 44 / cohort 1946

Distance 64.99 pc · percentile 15 / cohort 1975

ESI 0.750 · percentile 97 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

13.077 days

Semi-major axis

— AU

Eccentricity

0.092

Inclination

— °

Year Length

A year here lasts approximately 13.08 Earth days (3.6% of a terrestrial year) on a nearly circular orbit.

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.750

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Gandolfi et al. 2025

Instrument

HARPS Spectrograph

Publication

2025-09

Observation locale

Ground

Discovery cohort

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

Proxima Cen d · Rocky Terrestrial 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: TOI-1203

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,737 K — cooler than the Sun (5,778 K)

Estimated Age

12.50 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.179 R☉

Stellar Mass

0.886 M☉

Metallicity [Fe/H]

-0.39

Extended Stellar Properties

Surface gravity (log g)

4.340 dex

Stellar density

0.767 g/cm³

Systemic radial velocity

72.66 km/s

Rotational v·sin i

1.40 km/s

Activity index (log R'HK)

-4.998

Metallicity ratio

[Fe/H]

Distance

64.99 parsec

Light-years 211.98 ly

V-band magnitude

8.59 mag

Voyager-speed travel 3,738,317 yr

Multi-band Host Photometry — 7 bands

Astrometric Data

Parallax

15.357 mas

Total Proper Motion

296.334 mas/yr

PM Right Ascension

292.93 mas/yr

PM Declination

-44.78 mas/yr

Galactic Cartesian (pc)

x = -0.808 · y = 0.168 · z = -0.565

Equatorial (J2000)

RA 168.22674° · Dec -34.40694°

Galactic ℓ, b

280.785° · 24.192°

Ecliptic λ, β

184.972° · -35.831°

HTM-20 index

-493628253