Key parameters at a glance

A radius of 2.74 Earth radii
A mass of 317.83 Earth masses
Surface gravity around 42.33 g
An orbital period of 4.938 days
Semi-major axis 0.0574 AU
Equilibrium temperature 1,041 K (768 °C)
Distance from Earth 324.60 light-years
Earth Similarity Index 0.124
Travel time at Voyager 1 speed 5,724,325 years

TOI-251 b Planet Profile

Physical Specs

Radius

2.74 R⊕

Radius (Jupiter)

0.244 R♃

Mass

317.83 M⊕

Mass (Jupiter)

1.000 M♃

Density

— g/cm³

Surface Gravity

42.33 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.124

HZ Position Inner

Controversial No

Discovery

Year 2021

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#815of 1978

top 41.2%

This planet

2.74R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-212 c 2.74 R⊕ Kepler-192 b 2.74 R⊕ Kepler-1118 b 2.74 R⊕

Metric	Earth	TOI-251 b	Jupiter
Radius (R⊕)	1.00	2.74	11.21
Mass (M⊕)	1.00	317.83	317.83
Density (g/cm³)	5.51	—	1.33
Surface Gravity (g)	1.00	42.33	2.53
Insolation (S⊕)	1.00	277.75	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	317.830 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 224225541

Gaia DR2

Gaia DR2 6539037542941988736

Gaia DR3

Gaia DR3 6539037542941988736

System

TOI-251

Percentile among Sub-Neptune cohort

Radius 2.740 R⊕ · percentile 59 / cohort 1978

Mass 317.830 M⊕ · percentile 99 / cohort 1978

Orbital period 4.94 d · percentile 12 / cohort 1946

Distance 99.52 pc · percentile 20 / cohort 1975

ESI 0.124 · percentile 1 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

4.938 days

Semi-major axis

0.0574 AU

Eccentricity

0.000

Inclination

87.52 °

Year Length

A year here lasts approximately 4.94 Earth days (1.4% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0574 AU.

Transit Fingerprint

Depth

0.084 %

Duration

2.232 h

Impact parameter b

0.607

Rp / R★

0.028580

Transit midpoint (BJD)

2,458,357.3055

Photometric dip

Transit produces a flux drop of 845 ppm lasting ≈ 2.23 h.

Extended Orbital Architecture

Planet / star radius ratio

0.028580

Semi-major axis / stellar radius

14.020

Impact parameter (b)

0.607

RV semi-amplitude (K)

120.000 m/s

Transit mid-time (BJD)

2,458,357.3055

Angular separation (arcsec)

0.57700

Eq. Temperature

1,041K

(768 °C)

Insolation (S⊕)

277.75

Earth = 1.00

Earth Similarity (ESI)

0.124

0 = alien, 1 = Earth-identical

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

Discovery Paper

Primary reference

Zhou et al. 2021

Instrument

TESS CCD Array

Publication

2021-01

Observation locale

Space

Discovery cohort

Planets confirmed in 2021 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-2257 b · Sub-Neptune TOI-2285 b · Super-Earth TOI-1231 b · Sub-Neptune AU Mic c · Sub-Neptune LHS 1678 c · Rocky Terrestrial LHS 1478 b · Rocky Terrestrial TOI-2406 b · Sub-Neptune HD 207897 b · Sub-Neptune TOI-269 b · Sub-Neptune TIC 172900988 b · Gas Giant TOI-178 g · Sub-Neptune TOI-2076 d · Sub-Neptune

Host System: TOI-251

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,875 K — hotter than the Sun (5,778 K)

Estimated Age

0.18 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.881 R☉

Stellar Mass

1.036 M☉

Metallicity [Fe/H]

-0.11

Extended Stellar Properties

Surface gravity (log g)

4.560 dex

Stellar density

1.679 g/cm³

Systemic radial velocity

-2.06 km/s

Rotational v·sin i

11.50 km/s

Rotation period

3.84 days

Metallicity ratio

[Fe/H]

Distance

99.52 parsec

Light-years 324.60 ly

V-band magnitude

9.89 mag

Voyager-speed travel 5,724,325 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

10.019 mas

Total Proper Motion

44.680 mas/yr

PM Right Ascension

44.64 mas/yr

PM Declination

1.90 mas/yr

Galactic Cartesian (pc)

x = 0.790 · y = -0.096 · z = -0.605

Equatorial (J2000)

RA 353.06207° · Dec -37.25586°

Galactic ℓ, b

356.734° · -70.484°

Ecliptic λ, β

337.388° · -31.143°

HTM-20 index

517638592