Key parameters at a glance

A radius of 2.94 Earth radii
A mass of 55.30 Earth masses
Surface gravity around 6.40 g
An orbital period of 17.232 days
Semi-major axis 0.1350 AU
Equilibrium temperature 817 K (544 °C)
Distance from Earth 3,332.21 light-years
Earth Similarity Index 0.272
Travel time at Voyager 1 speed 58,763,439 years

1 sibling around Kepler-123

Kepler-123 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
Kepler-123 b this	Sub-Neptune	2.94	55.30	17.232	817	2014
Kepler-123 c	Super-Earth	1.48	2.79	26.695	706	2014

Kepler-123 b Planet Profile

Physical Specs

Radius

2.94 R⊕

Radius (Jupiter)

0.262 R♃

Mass

55.30 M⊕

Mass (Jupiter)

0.174 M♃

Density

12.00 g/cm³

Surface Gravity

6.40 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.272

HZ Position Inner

Controversial No

Discovery

Year 2014

Method Transit

Facility Kepler

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#570of 1978

top 28.8%

This planet

2.94R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-210 b 2.94 R⊕ Kepler-67 b 2.94 R⊕ Kepler-58 d 2.94 R⊕

Metric	Earth	Kepler-123 b	Jupiter
Radius (R⊕)	1.00	2.94	11.21
Mass (M⊕)	1.00	55.30	317.83
Density (g/cm³)	5.51	12.00	1.33
Surface Gravity (g)	1.00	6.40	2.53
Insolation (S⊕)	1.00	138.81	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	55.300 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 272944990

Gaia DR2

Gaia DR2 2078697552035948800

Gaia DR3

Gaia DR3 2078697552035948800

System

Kepler-123

Percentile among Sub-Neptune cohort

Radius 2.940 R⊕ · percentile 71 / cohort 1978

Mass 55.300 M⊕ · percentile 98 / cohort 1978

Orbital period 17.23 d · percentile 57 / cohort 1946

Distance 1,021.66 pc · percentile 79 / cohort 1975

ESI 0.272 · percentile 21 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

17.232 days

Semi-major axis

0.1350 AU

Eccentricity

0.000

Inclination

89.17 °

Year Length

A year here lasts approximately 17.23 Earth days (4.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1350 AU.

Transit Fingerprint

Depth

0.051 %

Duration

4.566 h

Impact parameter b

0.530

Rp / R★

0.020998

Transit midpoint (BJD)

2,454,968.0911

Photometric dip

Transit produces a flux drop of 510 ppm lasting ≈ 4.57 h.

Extended Orbital Architecture

Planet / star radius ratio

0.020998

Semi-major axis / stellar radius

29.070

Impact parameter (b)

0.530

Transit mid-time (BJD)

2,454,968.0911

Angular separation (arcsec)

0.13200

Eq. Temperature

817K

(544 °C)

Insolation (S⊕)

138.81

Earth = 1.00

Earth Similarity (ESI)

0.272

0 = alien, 1 = Earth-identical

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

Discovery Paper

Primary reference

Rowe et al. 2014

Instrument

Kepler CCD Array

Publication

2014-03

Observation locale

Space

Discovery cohort

Planets confirmed in 2014 at Kepler (12 shown).

Kepler-186 e · Super-Earth Kepler-395 c · Super-Earth Kepler-220 e · Super-Earth Kepler-249 d · Super-Earth Kepler-296 f · Super-Earth Kepler-367 c · Rocky Terrestrial Kepler-296 e · Super-Earth Kepler-155 c · Sub-Neptune Kepler-138 d · Super-Earth Kepler-333 c · Rocky Terrestrial Kepler-331 d · Super-Earth Kepler-267 d · Sub-Neptune

Host System: Kepler-123

Spectral Class

F-type yellow-white

Effective Temperature

6,089 K — hotter than the Sun (5,778 K)

Estimated Age

5.01 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.264 R☉

Stellar Mass

1.079 M☉

Metallicity [Fe/H]

-0.08

Extended Stellar Properties

Surface gravity (log g)

4.277 dex

Stellar density

0.490 g/cm³

Metallicity ratio

[Fe/H]

Distance

1,021.66 parsec

Light-years 3,332.21 ly

V-band magnitude

14.13 mag

Voyager-speed travel 58,763,439 yr

Multi-band Host Photometry — 16 bands

Astrometric Data

Parallax

0.950 mas

Total Proper Motion

1.170 mas/yr

PM Right Ascension

-0.35 mas/yr

PM Declination

1.12 mas/yr

Galactic Cartesian (pc)

x = 0.333 · y = -0.654 · z = 0.679

Equatorial (J2000)

RA 296.99859° · Dec 42.78196°

Galactic ℓ, b

76.888° · 8.635°

Ecliptic λ, β

315.287° · 62.042°

HTM-20 index

1601151001