Key parameters at a glance

A radius of 3.65 Earth radii
A mass of 15.40 Earth masses
Surface gravity around 1.16 g
An orbital period of 24.246 days
Semi-major axis 0.1288 AU
Equilibrium temperature 330 K (56 °C)
Distance from Earth 90.09 light-years
Earth Similarity Index 0.614
Travel time at Voyager 1 speed 1,588,792 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

This list of exoplanets discovered in 2021 is a list of confirmed exoplanets that were first observed in 2021. For exoplanets detected only by radial velocity, the listed value for mass is a lower limit. See Minimum mass for more information.

Excerpted from Wikipedia · full article

TOI-1231 b Planet Profile

Physical Specs

Radius

3.65 R⊕

Radius (Jupiter)

0.326 R♃

Mass

15.40 M⊕

Mass (Jupiter)

0.048 M♃

Density

1.74 g/cm³

Surface Gravity

1.16 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.614

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

#113of 1978

top 5.7%

This planet

3.65R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

WASP-47 d 3.65 R⊕ Kepler-967 c 3.65 R⊕ Kepler-1128 b 3.65 R⊕

Metric	Earth	TOI-1231 b	Jupiter
Radius (R⊕)	1.00	3.65	11.21
Mass (M⊕)	1.00	15.40	317.83
Density (g/cm³)	5.51	1.74	1.33
Surface Gravity (g)	1.00	1.16	2.53
Insolation (S⊕)	1.00	1.93	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	15.400 M⊕	Direct mass measurement (not derived).
Minimum mass (M sin i)	15.400 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

TIC

TIC 447061717

Gaia DR2

Gaia DR2 5357465071715078016

Gaia DR3

Gaia DR3 5357465071731312768

System

TOI-1231

Percentile among Sub-Neptune cohort

Radius 3.650 R⊕ · percentile 94 / cohort 1978

Mass 15.400 M⊕ · percentile 93 / cohort 1978

Orbital period 24.25 d · percentile 68 / cohort 1946

Distance 27.62 pc · percentile 7 / cohort 1975

ESI 0.614 · percentile 84 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

24.246 days

Semi-major axis

0.1288 AU

Eccentricity

0.087

Inclination

89.73 °

Year Length

A year here lasts approximately 24.25 Earth days (6.6% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1288 AU.

Transit Fingerprint

Depth

0.492 %

Duration

3.240 h

Impact parameter b

0.270

Rp / R★

0.070100

Transit midpoint (BJD)

2,458,685.1163

Photometric dip

Transit produces a flux drop of 4,920 ppm lasting ≈ 3.24 h.

Extended Orbital Architecture

Planet / star radius ratio

0.070100

Semi-major axis / stellar radius

58.100

Impact parameter (b)

0.270

RV semi-amplitude (K)

5.600 m/s

Transit mid-time (BJD)

2,458,685.1163

Long. of periastron (ω)

176.00°

Angular separation (arcsec)

4.66000

Eq. Temperature

330K

(56 °C)

Insolation (S⊕)

1.93

Earth = 1.00

Earth Similarity (ESI)

0.614

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — liquid water is physically possible with adequate atmospheric pressure. 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

Burt et al. 2021

Instrument

TESS CCD Array

Publication

2021-09

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 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 TOI-1749 d · Sub-Neptune

Host System: TOI-1231

Spectral Class

M-type red dwarf

Effective Temperature

3,553 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.476 R☉

Stellar Mass

0.485 M☉

Metallicity [Fe/H]

0.04

Extended Stellar Properties

Surface gravity (log g)

4.767 dex

Stellar density

6.310 g/cm³

Metallicity ratio

[Fe/H]

Distance

27.62 parsec

Light-years 90.09 ly

V-band magnitude

12.36 mag

Voyager-speed travel 1,588,792 yr

Multi-band Host Photometry — 7 bands

Astrometric Data

Parallax

36.174 mas

Total Proper Motion

372.406 mas/yr

PM Right Ascension

-89.05 mas/yr

PM Declination

361.60 mas/yr

Galactic Cartesian (pc)

x = -0.560 · y = 0.241 · z = -0.793

Equatorial (J2000)

RA 156.74726° · Dec -52.46787°

Galactic ℓ, b

281.826° · 4.382°

Ecliptic λ, β

189.607° · -55.411°

HTM-20 index

886087256

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