Key parameters at a glance

A radius of 0.53 Earth radii
A mass of 0.20 Earth masses
Surface gravity around 0.71 g
An orbital period of 6.189 days
Semi-major axis 0.0600 AU
Equilibrium temperature 783 K (510 °C)
Distance from Earth 118.85 light-years
Earth Similarity Index 0.361
Travel time at Voyager 1 speed 2,095,919 years
Almost certainly tidally locked to its host star given the close orbit

4 siblings around Kepler-444

Kepler-444 d shares its host star with 4 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
Kepler-444 b	Rocky Terrestrial	0.40	0.04	3.600	938	2015
Kepler-444 c	Rocky Terrestrial	0.50	0.08	4.546	868	2015
Kepler-444 d this	Rocky Terrestrial	0.53	0.20	6.189	783	2015
Kepler-444 e	Rocky Terrestrial	0.55	0.10	7.743	727	2015
Kepler-444 f	Rocky Terrestrial	0.74	0.33	9.740	673	2015

Kepler-444 d Planet Profile

Physical Specs

Radius

0.53 R⊕

Radius (Jupiter)

0.047 R♃

Mass

0.20 M⊕

Mass (Jupiter)

0.001 M♃

Density

7.90 g/cm³

Surface Gravity

0.71 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.361

HZ Position Inner

Controversial No

Discovery

Year 2015

Method Transit

Facility Kepler

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#558of 570

top 97.7%

This planet

0.53R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-62 c 0.54 R⊕ Kepler-1308 b 0.52 R⊕ Kepler-444 e 0.55 R⊕

Metric	Earth	Kepler-444 d	Jupiter
Radius (R⊕)	1.00	0.53	11.21
Mass (M⊕)	1.00	0.20	317.83
Density (g/cm³)	5.51	7.90	1.33
Surface Gravity (g)	1.00	0.71	2.53
Insolation (S⊕)	1.00	109.64	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	0.200 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HIP

HIP 94931

TIC

TIC 394172596

Gaia DR2

Gaia DR2 2101486923385239808

Gaia DR3

Gaia DR3 2101486923385239808

System

Kepler-444

Percentile among Rocky Terrestrial cohort

Radius 0.530 R⊕ · percentile 2 / cohort 570

Mass 0.200 M⊕ · percentile 4 / cohort 570

Orbital period 6.19 d · percentile 62 / cohort 567

Distance 36.44 pc · percentile 15 / cohort 566

ESI 0.361 · percentile 53 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

6.189 days

Semi-major axis

0.0600 AU

Eccentricity

0.180

Inclination

88.16 °

Year Length

A year here lasts approximately 6.19 Earth days (1.7% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0600 AU.

Transit Fingerprint

Depth

0.005 %

Duration

2.211 h

Impact parameter b

0.530

Rp / R★

0.006440

Transit midpoint (BJD)

2,454,967.7869

Photometric dip

Transit produces a flux drop of 48 ppm lasting ≈ 2.21 h.

Extended Orbital Architecture

Planet / star radius ratio

0.006440

Semi-major axis / stellar radius

17.151

Impact parameter (b)

0.530

Transit mid-time (BJD)

2,454,967.7869

Angular separation (arcsec)

1.65000

Eq. Temperature

783K

(510 °C)

Insolation (S⊕)

109.64

Earth = 1.00

Earth Similarity (ESI)

0.361

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.

Discovery Paper

Primary reference

Campante et al. 2015

Instrument

Kepler CCD Array

Publication

2015-02

Observation locale

Space

Discovery cohort

Planets confirmed in 2015 at Kepler (12 shown).

Kepler-438 b · Rocky Terrestrial Kepler-445 d · Super-Earth Kepler-442 b · Super-Earth Kepler-439 b · Sub-Neptune Kepler-437 b · Sub-Neptune Kepler-440 b · Super-Earth KIC 8540376 c · Sub-Neptune Kepler-445 b · Super-Earth Kepler-446 d · Super-Earth Kepler-436 b · Sub-Neptune Kepler-445 c · Sub-Neptune Kepler-443 b · Sub-Neptune

Host System: Kepler-444

Spectral Class

K-type orange

Effective Temperature

5,046 K — cooler than the Sun (5,778 K)

Estimated Age

11.23 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.752 R☉

Stellar Mass

0.758 M☉

Metallicity [Fe/H]

-0.55

Extended Stellar Properties

Surface gravity (log g)

4.563 dex

Stellar density

2.493 g/cm³

Systemic radial velocity

-121.90 km/s

Rotational v·sin i

2.00 km/s

Metallicity ratio

[Fe/H]

Distance

36.44 parsec

Light-years 118.85 ly

V-band magnitude

8.87 mag

Voyager-speed travel 2,095,919 yr

Multi-band Host Photometry — 15 bands

Astrometric Data

Parallax

27.414 mas

Total Proper Motion

639.253 mas/yr

PM Right Ascension

94.68 mas/yr

PM Declination

-632.20 mas/yr

Galactic Cartesian (pc)

x = 0.253 · y = -0.703 · z = 0.664

Equatorial (J2000)

RA 289.75283° · Dec 41.63188°

Galactic ℓ, b

73.361° · 12.891°

Ecliptic λ, β

303.531° · 62.790°

HTM-20 index

-1506167882