Key parameters at a glance

A radius of 1.52 Earth radii
A mass of 3.51 Earth masses
Surface gravity around 1.52 g
An orbital period of 4.157 days
Semi-major axis 0.0487 AU
Equilibrium temperature 1,361 K (1088 °C)
Distance from Earth 211.98 light-years
Earth Similarity Index 0.214
Travel time at Voyager 1 speed 3,738,317 years

3 siblings around TOI-1203

TOI-1203 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
TOI-1203 b this	Super-Earth	1.52	3.51	4.157	1,361	2025
TOI-1203 c	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 b Planet Profile

Physical Specs

Radius

1.52 R⊕

Radius (Jupiter)

0.136 R♃

Mass

3.51 M⊕

Mass (Jupiter)

0.011 M♃

Density

5.48 g/cm³

Surface Gravity

1.52 g (Earth)

Classification

Planet Type

Super-Earth

ESI Score 0.214

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

#707of 1176

top 60.0%

This planet

1.52R⊕

Super-Earth median

1.60R⊕

Nearest-size peers

Kepler-65 d 1.52 R⊕ Kepler-348 b 1.52 R⊕ Kepler-306 b 1.52 R⊕

Metric	Earth	TOI-1203 b	Jupiter
Radius (R⊕)	1.00	1.52	11.21
Mass (M⊕)	1.00	3.51	317.83
Density (g/cm³)	5.51	5.48	1.33
Surface Gravity (g)	1.00	1.52	2.53
Insolation (S⊕)	1.00	572.20	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	3.510 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HIP

HIP 54779

TIC

TIC 23434737

Gaia DR2

Gaia DR2 5402390257832925952

Gaia DR3

Gaia DR3 5402390257832925952

System

TOI-1203

Percentile among Super-Earth cohort

Radius 1.520 R⊕ · percentile 39 / cohort 1176

Mass 3.510 M⊕ · percentile 59 / cohort 1176

Orbital period 4.16 d · percentile 33 / cohort 1164

Distance 64.99 pc · percentile 13 / cohort 1171

ESI 0.214 · percentile 16 / cohort 1176

Orbit & Habitability

Orbital Dynamics

Period

4.157 days

Semi-major axis

0.0487 AU

Eccentricity

0.067

Inclination

84.29 °

Year Length

A year here lasts approximately 4.16 Earth days (1.1% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0487 AU.

Transit Fingerprint

Duration

1.911 h

Impact parameter b

0.847

Rp / R★

0.011820

Transit midpoint (BJD)

2,458,545.8916

Extended Orbital Architecture

Planet / star radius ratio

0.011820

Semi-major axis / stellar radius

8.880

Impact parameter (b)

0.847

RV semi-amplitude (K)

1.510 m/s

Transit mid-time (BJD)

2,458,545.8916

Long. of periastron (ω)

125.40°

Angular separation (arcsec)

0.74900

Eq. Temperature

1,361K

(1088 °C)

Insolation (S⊕)

572.20

Earth = 1.00

Earth Similarity (ESI)

0.214

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.

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

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 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

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