Key parameters at a glance

A radius of 2.64 Earth radii
A mass of 6.70 Earth masses
Surface gravity around 0.96 g
An orbital period of 5.198 days
Semi-major axis 0.0554 AU
Equilibrium temperature 922 K (649 °C)
Distance from Earth 243.95 light-years
Earth Similarity Index 0.264
Travel time at Voyager 1 speed 4,302,139 years

1 sibling around TOI-421

TOI-421 b 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-421 b this	Sub-Neptune	2.64	6.70	5.198	922	2020
TOI-421 c	Neptune-like	5.09	14.10	16.068	635	2020

TOI-421 b Planet Profile

Physical Specs

Radius

2.64 R⊕

Radius (Jupiter)

0.236 R♃

Mass

6.70 M⊕

Mass (Jupiter)

0.021 M♃

Density

2.04 g/cm³

Surface Gravity

0.96 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.264

HZ Position Inner

Controversial No

Discovery

Year 2020

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#958of 1978

top 48.4%

This planet

2.64R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-635 b 2.64 R⊕ Kepler-1134 b 2.64 R⊕ Kepler-571 b 2.64 R⊕

Metric	Earth	TOI-421 b	Jupiter
Radius (R⊕)	1.00	2.64	11.21
Mass (M⊕)	1.00	6.70	317.83
Density (g/cm³)	5.51	2.04	1.33
Surface Gravity (g)	1.00	0.96	2.53
Insolation (S⊕)	1.00	154.57	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	6.700 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 94986319

Gaia DR2

Gaia DR2 2984582227215748864

Gaia DR3

Gaia DR3 2984582227215748864

System

TOI-421

Percentile among Sub-Neptune cohort

Radius 2.640 R⊕ · percentile 51 / cohort 1978

Mass 6.700 M⊕ · percentile 36 / cohort 1978

Orbital period 5.20 d · percentile 13 / cohort 1946

Distance 74.80 pc · percentile 16 / cohort 1975

ESI 0.264 · percentile 20 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

5.198 days

Semi-major axis

0.0554 AU

Eccentricity

0.130

Inclination

85.68 °

Year Length

A year here lasts approximately 5.20 Earth days (1.4% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0554 AU.

Transit Fingerprint

Depth

0.044 %

Duration

1.090 h

Impact parameter b

0.942

Rp / R★

0.027900

Transit midpoint (BJD)

2,459,189.7341

Photometric dip

Transit produces a flux drop of 437 ppm lasting ≈ 1.09 h.

Extended Orbital Architecture

Planet / star radius ratio

0.027900

Impact parameter (b)

0.942

RV semi-amplitude (K)

2.830 m/s

Transit mid-time (BJD)

2,459,189.7341

Long. of periastron (ω)

140.00°

Angular separation (arcsec)

0.74100

Eq. Temperature

922K

(649 °C)

Insolation (S⊕)

154.57

Earth = 1.00

Earth Similarity (ESI)

0.264

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.

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

Carleo et al. 2020

Instrument

TESS CCD Array

Publication

2020-09

Observation locale

Space

Discovery cohort

Planets confirmed in 2020 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-700 d · Rocky Terrestrial TOI-237 b · Super-Earth TOI-700 b · Rocky Terrestrial TOI-1266 c · Super-Earth LTT 3780 c · Sub-Neptune TOI-700 c · Sub-Neptune TOI-776 c · Sub-Neptune TOI-942 c · Neptune-like TOI-776 b · Super-Earth TOI-1266 b · Sub-Neptune TOI-540 b · Rocky Terrestrial LHS 1815 b · Rocky Terrestrial

Host System: TOI-421

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,291 K — cooler than the Sun (5,778 K)

Estimated Age

10.90 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.866 R☉

Stellar Mass

0.833 M☉

Metallicity [Fe/H]

-0.04

Extended Stellar Properties

Surface gravity (log g)

4.480 dex

Stellar density

1.805 g/cm³

Systemic radial velocity

79.54 km/s

Rotational v·sin i

1.80 km/s

Rotation period

39.60 days

Metallicity ratio

[Fe/H]

Distance

74.80 parsec

Light-years 243.95 ly

V-band magnitude

9.93 mag

Voyager-speed travel 4,302,139 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

13.341 mas

Total Proper Motion

61.796 mas/yr

PM Right Ascension

-35.69 mas/yr

PM Declination

50.45 mas/yr

Galactic Cartesian (pc)

x = 0.137 · y = 0.959 · z = -0.247

Equatorial (J2000)

RA 81.85328° · Dec -14.27674°

Galactic ℓ, b

216.794° · -24.937°

Ecliptic λ, β

80.037° · -37.435°

HTM-20 index

1761619293