Key parameters at a glance

A radius of 2.86 Earth radii
A mass of 5.00 Earth masses
Surface gravity around 0.61 g
An orbital period of 12.928 days
Semi-major axis 0.1009 AU
Equilibrium temperature 718 K (445 °C)
Distance from Earth 66.73 light-years
Earth Similarity Index 0.307
Travel time at Voyager 1 speed 1,176,701 years
Almost certainly tidally locked to its host star given the close orbit

3 siblings around TOI-5789

TOI-5789 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-5789 b	Super-Earth	1.26	2.12	2.764	1,201	2026
TOI-5789 c this	Sub-Neptune	2.86	5.00	12.928	718	—
TOI-5789 d	Super-Earth	1.91	4.29	29.650	545	2026
TOI-5789 e	Sub-Neptune	3.43	11.61	62.980	424	2026

TOI-5789 c Planet Profile

Physical Specs

Radius

2.86 R⊕

Radius (Jupiter)

0.255 R♃

Mass

5.00 M⊕

Mass (Jupiter)

0.016 M♃

Density

1.16 g/cm³

Surface Gravity

0.61 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.307

HZ Position Inner

Controversial No

Discovery

Year —

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#671of 1978

top 33.9%

This planet

2.86R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-58 c 2.86 R⊕ Kepler-142 c 2.86 R⊕ Kepler-170 c 2.86 R⊕

Metric	Earth	TOI-5789 c	Jupiter
Radius (R⊕)	1.00	2.86	11.21
Mass (M⊕)	1.00	5.00	317.83
Density (g/cm³)	5.51	1.16	1.33
Surface Gravity (g)	1.00	0.61	2.53
Insolation (S⊕)	1.00	8.72	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	5.000 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HD 191785

HIP

HIP 99452

TIC

TIC 87216634

Gaia DR2

Gaia DR2 1809360187271699584

System

TOI-5789

Percentile among Sub-Neptune cohort

Radius 2.860 R⊕ · percentile 66 / cohort 1978

Mass 5.000 M⊕ · percentile 8 / cohort 1978

Orbital period 12.93 d · percentile 44 / cohort 1946

Distance 20.46 pc · percentile 4 / cohort 1975

ESI 0.307 · percentile 30 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

12.928 days

Semi-major axis

0.1009 AU

Eccentricity

0.067

Inclination

88.02 °

Year Length

A year here lasts approximately 12.93 Earth days (3.5% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1009 AU.

Transit Fingerprint

Depth

0.079 %

Duration

2.019 h

Impact parameter b

0.903

Rp / R★

0.031400

Transit midpoint (BJD)

2,460,151.1587

Photometric dip

Transit produces a flux drop of 790 ppm lasting ≈ 2.02 h.

Extended Orbital Architecture

Planet / star radius ratio

0.031400

Impact parameter (b)

0.903

RV semi-amplitude (K)

1.560 m/s

Transit mid-time (BJD)

2,460,151.1587

Angular separation (arcsec)

4.93000

Eq. Temperature

718K

(445 °C)

Insolation (S⊕)

8.72

Earth = 1.00

Earth Similarity (ESI)

0.307

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

Bonomo et al. 2025

Instrument

TESS CCD Array

Publication

2025-10

Observation locale

Space

Host System: TOI-5789

Spectral Class

K-type orange

Effective Temperature

5,185 K — cooler than the Sun (5,778 K)

Estimated Age

9.40 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.833 R☉

Stellar Mass

0.821 M☉

Metallicity [Fe/H]

-0.12

Extended Stellar Properties

Surface gravity (log g)

4.511 dex

Stellar density

2.000 g/cm³

Systemic radial velocity

-49.32 km/s

Rotational v·sin i

1.20 km/s

Activity index (log R'HK)

-5.153

Metallicity ratio

[Fe/H]

Distance

20.46 parsec

Light-years 66.73 ly

V-band magnitude

7.35 mag

Voyager-speed travel 1,176,701 yr

Multi-band Host Photometry — 7 bands

Astrometric Data

Parallax

48.852 mas

Total Proper Motion

575.094 mas/yr

PM Right Ascension

-414.66 mas/yr

PM Declination

398.48 mas/yr

Galactic Cartesian (pc)

x = 0.520 · y = -0.807 · z = 0.279

Equatorial (J2000)

RA 302.77345° · Dec 16.18971°

Galactic ℓ, b

56.682° · -9.438°

Ecliptic λ, β

309.527° · 35.240°

HTM-20 index

1705062875

Observation Record

Photometric series

Stellar spectra

Archive notes

Similar Worlds

Kepler-1388 d

Sub-Neptune · K-type orange

Radius 2.86 R⊕ · 1,480.1 ly

Kepler-304 b

Sub-Neptune · K-type orange

Radius 2.86 R⊕ · 1,417.7 ly

HD 110067 d

Sub-Neptune · K-type orange

Radius 2.85 R⊕ · 104.9 ly

HIP 54373 b

Sub-Neptune · K-type orange

Radius 2.87 R⊕ · 61.0 ly

K2-199 c

Sub-Neptune · K-type orange

Radius 2.85 R⊕ · 350.7 ly

Kepler-1684 b

Sub-Neptune · K-type orange

Radius 2.87 R⊕ · 2,028.7 ly

Explore Related Categories

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