Key parameters at a glance

A radius of 2.22 Earth radii
A mass of 5.56 Earth masses
Surface gravity around 1.13 g
An orbital period of 4.940 days
Semi-major axis 0.0538 AU
Equilibrium temperature 1,345 K (1071 °C)
Distance from Earth 223.33 light-years
Earth Similarity Index 0.188
Travel time at Voyager 1 speed 3,938,386 years

TOI-128.01 Planet Profile

Physical Specs

Radius

2.22 R⊕

Radius (Jupiter)

0.198 R♃

Mass

5.56 M⊕

Mass (Jupiter)

0.018 M♃

Density

2.80 g/cm³

Surface Gravity

1.13 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.188

HZ Position Inner

Controversial No

Discovery

Year 2024

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#1653of 1978

top 83.5%

This planet

2.22R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-1949 b 2.22 R⊕ KMT-2018-BLG-1988L b 2.22 R⊕ Kepler-1151 b 2.22 R⊕

Metric	Earth	TOI-128.01	Jupiter
Radius (R⊕)	1.00	2.22	11.21
Mass (M⊕)	1.00	5.56	317.83
Density (g/cm³)	5.51	2.80	1.33
Surface Gravity (g)	1.00	1.13	2.53
Insolation (S⊕)	1.00	182.41	0.037

Star Catalogue Identifiers

HIP

HIP 24718

TIC

TIC 391949880

Gaia DR2

Gaia DR2 4621607053580909568

Gaia DR3

Gaia DR3 4621607053580909568

System

TOI-128

Percentile among Sub-Neptune cohort

Radius 2.219 R⊕ · percentile 16 / cohort 1978

Mass 5.560 M⊕ · percentile 17 / cohort 1978

Orbital period 4.94 d · percentile 12 / cohort 1946

Distance 68.47 pc · percentile 15 / cohort 1975

ESI 0.188 · percentile 5 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

4.940 days

Semi-major axis

0.0538 AU

Eccentricity

—

Inclination

— °

Year Length

A year here lasts approximately 4.94 Earth days (1.4% of a terrestrial year) at a mean orbital distance of 0.0538 AU.

Transit Fingerprint

Depth

0.046 %

Duration

1.966 h

Rp / R★

0.017988

Transit midpoint (BJD)

2,460,175.8672

Photometric dip

Transit produces a flux drop of 455 ppm lasting ≈ 1.97 h.

Extended Orbital Architecture

Planet / star radius ratio

0.017988

Semi-major axis / stellar radius

10.245

Transit mid-time (BJD)

2,460,175.8672

Angular separation (arcsec)

0.78600

Eq. Temperature

1,345K

(1071 °C)

Insolation (S⊕)

182.41

Earth = 1.00

Earth Similarity (ESI)

0.188

0 = alien, 1 = Earth-identical

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

Discovery Paper

Primary reference

Hord et al. 2024

Instrument

TESS CCD Array

Publication

2024-05

Observation locale

Space

Discovery cohort

Planets confirmed in 2024 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

Gliese 12 b · Rocky Terrestrial TOI-6002 b · Super-Earth TOI-5713 b · Super-Earth TOI-4336 A b · Sub-Neptune TOI-406.01 · Sub-Neptune TOI-1224 c · Sub-Neptune LHS 1678 d · Rocky Terrestrial TOI-2088 b · Sub-Neptune TOI-2120 b · Sub-Neptune TOI-1806.01 · Sub-Neptune TOI-4633 c · Sub-Neptune TOI-260 b · Super-Earth

Host System: TOI-128

Spectral Class

F-type yellow-white

Effective Temperature

6,086 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.130 R☉

Stellar Mass

0.852 M☉

Metallicity [Fe/H]

—

Distance

68.47 parsec

Light-years 223.33 ly

V-band magnitude

8.44 mag

Voyager-speed travel 3,938,386 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

14.575 mas

Total Proper Motion

66.843 mas/yr

PM Right Ascension

-49.15 mas/yr

PM Declination

45.31 mas/yr

Galactic Cartesian (pc)

x = 0.029 · y = 0.154 · z = -0.988

Equatorial (J2000)

RA 79.52094° · Dec -80.96438°

Galactic ℓ, b

293.310° · -30.378°

Ecliptic λ, β

276.484° · -75.358°

HTM-20 index

360588065