Key parameters at a glance

A radius of 5.09 Earth radii
A mass of 14.10 Earth masses
Surface gravity around 0.54 g
An orbital period of 16.068 days
Semi-major axis 0.1170 AU
Equilibrium temperature 635 K (362 °C)
Distance from Earth 243.95 light-years
Earth Similarity Index 0.271
Travel time at Voyager 1 speed 4,302,139 years

1 sibling around TOI-421

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

TOI-421 c Planet Profile

Physical Specs

Radius

5.09 R⊕

Radius (Jupiter)

0.454 R♃

Mass

14.10 M⊕

Mass (Jupiter)

0.044 M♃

Density

0.59 g/cm³

Surface Gravity

0.54 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.271

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

#371of 574

top 64.5%

This planet

5.09R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

TOI-6651 b 5.09 R⊕ K2-398 c 5.10 R⊕ V1298 Tau c 5.08 R⊕

Metric	Earth	TOI-421 c	Jupiter
Radius (R⊕)	1.00	5.09	11.21
Mass (M⊕)	1.00	14.10	317.83
Density (g/cm³)	5.51	0.59	1.33
Surface Gravity (g)	1.00	0.54	2.53
Insolation (S⊕)	1.00	34.32	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	14.100 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 Neptune-like cohort

Radius 5.090 R⊕ · percentile 35 / cohort 574

Mass 14.100 M⊕ · percentile 6 / cohort 574

Orbital period 16.07 d · percentile 47 / cohort 524

Distance 74.80 pc · percentile 20 / cohort 572

ESI 0.271 · percentile 43 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

16.068 days

Semi-major axis

0.1170 AU

Eccentricity

0.190

Inclination

88.35 °

Year Length

A year here lasts approximately 16.07 Earth days (4.4% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.1170 AU.

Transit Fingerprint

Depth

0.293 %

Duration

2.755 h

Impact parameter b

0.700

Rp / R★

0.054000

Transit midpoint (BJD)

2,459,195.3074

Photometric dip

Transit produces a flux drop of 2,930 ppm lasting ≈ 2.76 h.

Extended Orbital Architecture

Planet / star radius ratio

0.054000

Semi-major axis / stellar radius

29.910

Impact parameter (b)

0.700

RV semi-amplitude (K)

4.100 m/s

Transit mid-time (BJD)

2,459,195.3074

Long. of periastron (ω)

102.00°

Angular separation (arcsec)

1.56000

Eq. Temperature

635K

(362 °C)

Insolation (S⊕)

34.32

Earth = 1.00

Earth Similarity (ESI)

0.271

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