Key parameters at a glance

A radius of 1.90 Earth radii
A mass of 4.00 Earth masses
Surface gravity around 1.11 g
An orbital period of 5.746 days
Semi-major axis 0.0418 AU
Equilibrium temperature 441 K (167 °C)
Distance from Earth 91.09 light-years
Earth Similarity Index 0.607
Travel time at Voyager 1 speed 1,606,329 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

G 9-40 b is a sub-Neptune exoplanet that has an orbital period of 5.7 days. The host star is a red dwarf located in the constellation Cancer 91 light-years away from Earth. The planet was discovered in 2019. The planet's density is too low for a rocky composition, suggesting that it is either water-rich or has a significant hydrogen atmosphere.

Excerpted from Wikipedia · full article

G 9-40 b Planet Profile

Physical Specs

Radius

1.90 R⊕

Radius (Jupiter)

0.170 R♃

Mass

4.00 M⊕

Mass (Jupiter)

0.013 M♃

Density

3.20 g/cm³

Surface Gravity

1.11 g (Earth)

Classification

Planet Type

Super-Earth

ESI Score 0.607

HZ Position Inner

Controversial No

Discovery

Year 2019

Method Transit

Facility K2

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#125of 1176

top 10.5%

This planet

1.90R⊕

Super-Earth median

1.60R⊕

Nearest-size peers

Kepler-158 c 1.90 R⊕ Kepler-349 b 1.90 R⊕ Kepler-196 b 1.90 R⊕

Metric	Earth	G 9-40 b	Jupiter
Radius (R⊕)	1.00	1.90	11.21
Mass (M⊕)	1.00	4.00	317.83
Density (g/cm³)	5.51	3.20	1.33
Surface Gravity (g)	1.00	1.11	2.53
Insolation (S⊕)	1.00	6.27	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	4.000 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 203214081

Gaia DR2

Gaia DR2 684992690384102528

Gaia DR3

Gaia DR3 684992690384102528

System

G 9-40

Percentile among Super-Earth cohort

Radius 1.900 R⊕ · percentile 88 / cohort 1176

Mass 4.000 M⊕ · percentile 73 / cohort 1176

Orbital period 5.75 d · percentile 45 / cohort 1164

Distance 27.93 pc · percentile 6 / cohort 1171

ESI 0.607 · percentile 81 / cohort 1176

Orbit & Habitability

Orbital Dynamics

Period

5.746 days

Semi-major axis

0.0418 AU

Eccentricity

0.000

Inclination

89.03 °

Year Length

A year here lasts approximately 5.75 Earth days (1.6% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0418 AU.

Transit Fingerprint

Depth

0.365 %

Duration

1.693 h

Impact parameter b

0.513

Rp / R★

0.057500

Transit midpoint (BJD)

2,459,503.3268

Photometric dip

Transit produces a flux drop of 3,650 ppm lasting ≈ 1.69 h.

Extended Orbital Architecture

Planet / star radius ratio

0.057500

Semi-major axis / stellar radius

30.460

Impact parameter (b)

0.513

RV semi-amplitude (K)

3.220 m/s

Transit mid-time (BJD)

2,459,503.3268

Long. of periastron (ω)

90.00°

Angular separation (arcsec)

1.50000

Eq. Temperature

441K

(167 °C)

Insolation (S⊕)

6.27

Earth = 1.00

Earth Similarity (ESI)

0.607

0 = alien, 1 = Earth-identical

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

Stefansson et al. 2020

Instrument

Kepler CCD Array

Publication

2020-03

Observation locale

Space

Discovery cohort

Planets confirmed in 2019 at K2 (12 shown).

EPIC 206032309 b · Rocky Terrestrial EPIC 201833600 c · Rocky Terrestrial EPIC 206215704 b · Rocky Terrestrial EPIC 201754305 d · Rocky Terrestrial EPIC 201841433 b · Rocky Terrestrial EPIC 206317286 b · Rocky Terrestrial EPIC 201615463 c · Rocky Terrestrial EPIC 212499991 b · Super-Earth EPIC 220554210 c · Super-Earth EPIC 201497682 b · Rocky Terrestrial K2-133 e · Super-Earth EPIC 206024342 b · Super-Earth

Host System: G 9-40

Spectral Class

M-type red dwarf

Effective Temperature

3,395 K — cooler than the Sun (5,778 K)

Estimated Age

9.90 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.303 R☉

Stellar Mass

0.295 M☉

Metallicity [Fe/H]

-0.07

Extended Stellar Properties

Surface gravity (log g)

4.840 dex

Stellar density

1.620 g/cm³

Systemic radial velocity

14.65 km/s

Rotational v·sin i

2.00 km/s

Rotation period

30.00 days

Metallicity ratio

[Fe/H]

Distance

27.93 parsec

Light-years 91.09 ly

V-band magnitude

13.82 mag

Voyager-speed travel 1,606,329 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

35.778 mas

Total Proper Motion

363.630 mas/yr

PM Right Ascension

175.51 mas/yr

PM Declination

-318.47 mas/yr

Galactic Cartesian (pc)

x = -0.657 · y = 0.663 · z = 0.360

Equatorial (J2000)

RA 134.71885° · Dec 21.07480°

Galactic ℓ, b

206.065° · 37.036°

Ecliptic λ, β

131.144° · 3.794°

HTM-20 index

-17473734

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