Key parameters at a glance

A radius of 2.75 Earth radii
A mass of 10.60 Earth masses
Surface gravity around 1.40 g
An orbital period of 9.428 days
Semi-major axis 0.0830 AU
Equilibrium temperature 794 K (521 °C)
Distance from Earth 360.44 light-years
Earth Similarity Index 0.321
Travel time at Voyager 1 speed 6,356,443 years
Almost certainly tidally locked to its host star given the close orbit

1 sibling around TOI-1438

TOI-1438 c 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
TOI-1438 b	Sub-Neptune	3.04	9.40	5.140	971	2025
TOI-1438 c this	Sub-Neptune	2.75	10.60	9.428	794	2025

TOI-1438 c Planet Profile

Physical Specs

Radius

2.75 R⊕

Radius (Jupiter)

0.245 R♃

Mass

10.60 M⊕

Mass (Jupiter)

0.033 M♃

Density

2.90 g/cm³

Surface Gravity

1.40 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.321

HZ Position Inner

Controversial No

Discovery

Year 2025

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#804of 1978

top 40.6%

This planet

2.75R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

TOI-2545 b 2.75 R⊕ HIP 97166 c 2.75 R⊕ Kepler-304 d 2.75 R⊕

Metric	Earth	TOI-1438 c	Jupiter
Radius (R⊕)	1.00	2.75	11.21
Mass (M⊕)	1.00	10.60	317.83
Density (g/cm³)	5.51	2.90	1.33
Surface Gravity (g)	1.00	1.40	2.53
Insolation (S⊕)	1.00	65.00	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	10.600 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 229650439

Gaia DR2

Gaia DR2 2268101727131230464

Gaia DR3

Gaia DR3 2268101727131230464

System

TOI-1438

Percentile among Sub-Neptune cohort

Radius 2.750 R⊕ · percentile 59 / cohort 1978

Mass 10.600 M⊕ · percentile 77 / cohort 1978

Orbital period 9.43 d · percentile 31 / cohort 1946

Distance 110.51 pc · percentile 22 / cohort 1975

ESI 0.321 · percentile 33 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

9.428 days

Semi-major axis

0.0830 AU

Eccentricity

0.000

Inclination

87.61 °

Year Length

A year here lasts approximately 9.43 Earth days (2.6% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0830 AU.

Transit Fingerprint

Depth

0.080 %

Duration

1.670 h

Impact parameter b

0.902

Rp / R★

0.030800

Transit midpoint (BJD)

2,458,689.9136

Photometric dip

Transit produces a flux drop of 799 ppm lasting ≈ 1.67 h.

Extended Orbital Architecture

Planet / star radius ratio

0.030800

Semi-major axis / stellar radius

21.600

Impact parameter (b)

0.902

RV semi-amplitude (K)

3.500 m/s

Transit mid-time (BJD)

2,458,689.9136

Long. of periastron (ω)

90.00°

Angular separation (arcsec)

0.75100

Eq. Temperature

794K

(521 °C)

Insolation (S⊕)

65.00

Earth = 1.00

Earth Similarity (ESI)

0.321

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

Persson et al. 2025

Instrument

TESS CCD Array

Publication

2025-08

Observation locale

Space

Discovery cohort

Planets confirmed in 2025 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-1266 d · Super-Earth TOI-2267 c · Rocky Terrestrial TOI-5799 c · Super-Earth TOI-5728 b · Super-Earth TOI-5716 b · Rocky Terrestrial TOI-7166 b · Sub-Neptune TOI-2267 b · Rocky Terrestrial TOI-2093 c · Sub-Neptune TOI-2267 d · Super-Earth TOI-5489 c · Super-Earth TOI-1743 b · Super-Earth TOI-4364 b · Sub-Neptune

Host System: TOI-1438

Spectral Class

K-type orange

Effective Temperature

5,230 K — cooler than the Sun (5,778 K)

Estimated Age

2.20 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.820 R☉

Stellar Mass

0.876 M☉

Metallicity [Fe/H]

0.03

Extended Stellar Properties

Surface gravity (log g)

4.500 dex

Stellar density

2.200 g/cm³

Systemic radial velocity

-29.40 km/s

Rotational v·sin i

1.80 km/s

Activity index (log R'HK)

-4.925

Metallicity ratio

[Fe/H]

Distance

110.51 parsec

Light-years 360.44 ly

V-band magnitude

10.96 mag

Voyager-speed travel 6,356,443 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

9.020 mas

Total Proper Motion

58.079 mas/yr

PM Right Ascension

-23.08 mas/yr

PM Declination

53.29 mas/yr

Galactic Cartesian (pc)

x = 0.049 · y = -0.255 · z = 0.966

Equatorial (J2000)

RA 280.92378° · Dec 74.93783°

Galactic ℓ, b

106.043° · 26.624°

Ecliptic λ, β

71.822° · 80.916°

HTM-20 index

1647446786

Similar Worlds

Kepler-304 d

Sub-Neptune · K-type orange

Radius 2.75 R⊕ · 1,417.7 ly

HIP 97166 c

Sub-Neptune · K-type orange

Radius 2.75 R⊕ · 215.1 ly

TOI-1824 b

Sub-Neptune · K-type orange

Radius 2.74 R⊕ · 193.8 ly

TOI-125 c

Sub-Neptune · K-type orange

Radius 2.76 R⊕ · 362.2 ly

TOI-1260 c

Sub-Neptune · K-type orange

Radius 2.76 R⊕ · 240.0 ly

K2-123 b

Sub-Neptune · K-type orange

Radius 2.76 R⊕ · 526.9 ly

Explore Related Categories

Sub-Neptune Planets Transit Discoveries Transiting Exoplanet Survey Satellite (TESS) Mission K-type orange Hosts