Key parameters at a glance

A radius of 3.52 Earth radii
A mass of 11.80 Earth masses
Surface gravity around 0.95 g
An orbital period of 4.773 days
Semi-major axis 0.0570 AU
Equilibrium temperature 1,242 K (969 °C)
Distance from Earth 426.79 light-years
Earth Similarity Index 0.171
Travel time at Voyager 1 speed 7,526,467 years

1 sibling around TOI-5398

TOI-5398 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-5398 c this	Sub-Neptune	3.52	11.80	4.773	1,242	2023
TOI-5398 b	Gas Giant	10.30	58.70	10.591	947	2022

TOI-5398 c Planet Profile

Physical Specs

Radius

3.52 R⊕

Radius (Jupiter)

0.314 R♃

Mass

11.80 M⊕

Mass (Jupiter)

0.037 M♃

Density

1.50 g/cm³

Surface Gravity

0.95 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.171

HZ Position Inner

Controversial No

Discovery

Year 2023

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#169of 1978

top 8.5%

This planet

3.52R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-657 b 3.52 R⊕ HD 45184 b 3.52 R⊕ Kepler-687 b 3.52 R⊕

Metric	Earth	TOI-5398 c	Jupiter
Radius (R⊕)	1.00	3.52	11.21
Mass (M⊕)	1.00	11.80	317.83
Density (g/cm³)	5.51	1.50	1.33
Surface Gravity (g)	1.00	0.95	2.53
Insolation (S⊕)	1.00	370.60	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	11.800 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 8260536

Gaia DR2

Gaia DR2 750888548244441344

Gaia DR3

Gaia DR3 750888548244441344

System

TOI-5398

Percentile among Sub-Neptune cohort

Radius 3.520 R⊕ · percentile 91 / cohort 1978

Mass 11.800 M⊕ · percentile 83 / cohort 1978

Orbital period 4.77 d · percentile 11 / cohort 1946

Distance 130.86 pc · percentile 24 / cohort 1975

ESI 0.171 · percentile 4 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

4.773 days

Semi-major axis

0.0570 AU

Eccentricity

0.140

Inclination

88.40 °

Year Length

A year here lasts approximately 4.77 Earth days (1.3% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0570 AU.

Transit Fingerprint

Depth

0.092 %

Duration

3.127 h

Impact parameter b

0.340

Rp / R★

0.030800

Transit midpoint (BJD)

2,459,628.6178

Photometric dip

Transit produces a flux drop of 920 ppm lasting ≈ 3.13 h.

Extended Orbital Architecture

Planet / star radius ratio

0.030800

Semi-major axis / stellar radius

11.800

Impact parameter (b)

0.340

RV semi-amplitude (K)

4.100 m/s

Transit mid-time (BJD)

2,459,628.6178

Long. of periastron (ω)

172.00°

Angular separation (arcsec)

0.43600

Eq. Temperature

1,242K

(969 °C)

Insolation (S⊕)

370.60

Earth = 1.00

Earth Similarity (ESI)

0.171

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

Mantovan et al. 2023

Instrument

TESS CCD Array

Publication

2023-10

Observation locale

Space

Discovery cohort

Planets confirmed in 2023 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-700 e · Rocky Terrestrial TOI-2095 c · Super-Earth TOI-715 b · Super-Earth TOI-2095 b · Super-Earth TOI-2096 c · Super-Earth TOI-1680 b · Super-Earth TOI-2096 b · Rocky Terrestrial TOI-904 c · Sub-Neptune TOI-1470 c · Sub-Neptune TOI-198 b · Super-Earth TOI-244 b · Super-Earth TOI-4184 b · Sub-Neptune

Host System: TOI-5398

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

6,000 K — hotter than the Sun (5,778 K)

Estimated Age

0.65 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.051 R☉

Stellar Mass

1.146 M☉

Metallicity [Fe/H]

0.09

Extended Stellar Properties

Surface gravity (log g)

4.440 dex

Stellar density

1.343 g/cm³

Systemic radial velocity

-9.95 km/s

Rotational v·sin i

7.50 km/s

Rotation period

7.34 days

Activity index (log R'HK)

-4.430

Metallicity ratio

[Fe/H]

Distance

130.86 parsec

Light-years 426.79 ly

V-band magnitude

10.06 mag

Voyager-speed travel 7,526,467 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

7.613 mas

Total Proper Motion

6.873 mas/yr

PM Right Ascension

1.33 mas/yr

PM Declination

6.74 mas/yr

Galactic Cartesian (pc)

x = -0.766 · y = 0.251 · z = 0.592

Equatorial (J2000)

RA 161.87956° · Dec 36.32943°

Galactic ℓ, b

185.821° · 62.233°

Ecliptic λ, β

148.696° · 26.351°

HTM-20 index

638923493