Key parameters at a glance

A radius of 1.64 Earth radii
A mass of 8.41 Earth masses
Surface gravity around 3.13 g
An orbital period of 1.593 days
Semi-major axis 0.0273 AU
Equilibrium temperature 2,026 K (1753 °C)
Distance from Earth 2,049.10 light-years
Earth Similarity Index 0.110
Travel time at Voyager 1 speed 36,135,839 years

2 siblings around Kepler-9

Kepler-9 d shares its host star with 2 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
Kepler-9 d this	Super-Earth	1.64	8.41	1.593	2,026	2010
Kepler-9 b	Neptune-like	8.29	43.40	19.239	661	2010
Kepler-9 c	Neptune-like	8.08	29.90	38.985	523	2010

Kepler-9 d Planet Profile

Physical Specs

Radius

1.64 R⊕

Radius (Jupiter)

0.146 R♃

Mass

8.41 M⊕

Mass (Jupiter)

0.026 M♃

Density

13.55 g/cm³

Surface Gravity

3.13 g (Earth)

Classification

Planet Type

Super-Earth

ESI Score 0.110

HZ Position Inner

Controversial No

Discovery

Year 2010

Method Transit

Facility Kepler

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#495of 1176

top 42.0%

This planet

1.64R⊕

Super-Earth median

1.60R⊕

Nearest-size peers

Kepler-46 d 1.64 R⊕ Kepler-179 b 1.64 R⊕ Kepler-247 b 1.64 R⊕

Metric	Earth	Kepler-9 d	Jupiter
Radius (R⊕)	1.00	1.64	11.21
Mass (M⊕)	1.00	8.41	317.83
Density (g/cm³)	5.51	13.55	1.33
Surface Gravity (g)	1.00	3.13	2.53
Insolation (S⊕)	1.00	1,339.66	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	8.415 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

TIC

TIC 120571842

Gaia DR2

Gaia DR2 2099925719951103872

Gaia DR3

Gaia DR3 2099925719951103872

System

Kepler-9

Percentile among Super-Earth cohort

Radius 1.640 R⊕ · percentile 56 / cohort 1176

Mass 8.415 M⊕ · percentile 95 / cohort 1176

Orbital period 1.59 d · percentile 9 / cohort 1164

Distance 628.26 pc · percentile 57 / cohort 1171

ESI 0.110 · percentile 1 / cohort 1176

Orbit & Habitability

Orbital Dynamics

Period

1.593 days

Semi-major axis

0.0273 AU

Eccentricity

0.000

Inclination

89.38 °

Year Length

A year here lasts approximately 1.59 Earth days (0.4% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0273 AU.

Transit Fingerprint

Depth

0.025 %

Duration

1.970 h

Impact parameter b

0.020

Rp / R★

0.014700

Transit midpoint (BJD)

2,455,015.0943

Photometric dip

Transit produces a flux drop of 248 ppm lasting ≈ 1.97 h.

Extended Orbital Architecture

Planet / star radius ratio

0.014700

Semi-major axis / stellar radius

5.540

Impact parameter (b)

0.020

RV semi-amplitude (K)

4.535 m/s

Transit mid-time (BJD)

2,455,015.0943

Angular separation (arcsec)

0.04350

Eq. Temperature

2,026K

(1753 °C)

Insolation (S⊕)

1,339.66

Earth = 1.00

Earth Similarity (ESI)

0.110

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.

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

Torres et al. 2011

Instrument

Kepler CCD Array

Publication

2011-01

Observation locale

Space

Discovery cohort

Planets confirmed in 2010 at Kepler (11 shown).

Kepler-11 g · Sub-Neptune Kepler-11 f · Sub-Neptune Kepler-11 d · Sub-Neptune Kepler-11 e · Neptune-like Kepler-11 b · Super-Earth Kepler-9 c · Neptune-like Kepler-11 c · Sub-Neptune Kepler-9 b · Neptune-like Kepler-40 b · Gas Giant Kepler-8 b · Gas Giant KOI-217 b · Gas Giant

Host System: Kepler-9

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,777 K — cooler than the Sun (5,778 K)

Estimated Age

1.00 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.020 R☉

Stellar Mass

1.070 M☉

Metallicity [Fe/H]

0.12

Extended Stellar Properties

Surface gravity (log g)

4.490 dex

Stellar density

1.150 g/cm³

Rotational v·sin i

1.90 km/s

Rotation period

16.49 days

Metallicity ratio

[Fe/H]

Distance

628.26 parsec

Light-years 2,049.10 ly

V-band magnitude

13.92 mag

Voyager-speed travel 36,135,839 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

1.563 mas

Total Proper Motion

14.922 mas/yr

PM Right Ascension

2.49 mas/yr

PM Declination

-14.71 mas/yr

Galactic Cartesian (pc)

x = 0.210 · y = -0.755 · z = 0.621

Equatorial (J2000)

RA 285.57399° · Dec 38.40082°

Galactic ℓ, b

68.980° · 14.490°

Ecliptic λ, β

295.275° · 60.481°

HTM-20 index

489015344