Key parameters at a glance

A radius of 0.73 Earth radii
A mass of 60.34 Earth masses
Surface gravity around 113.22 g
An orbital period of 0.453 days
Semi-major axis 0.0060 AU
Equilibrium temperature 720 K (447 °C)
Distance from Earth 130.66 light-years
Earth Similarity Index 0.185
Travel time at Voyager 1 speed 2,304,127 years
Almost certainly tidally locked to its host star given the close orbit

2 siblings around Kepler-42

Kepler-42 c 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-42 c this	Rocky Terrestrial	0.73	60.34	0.453	720	2011
Kepler-42 b	Rocky Terrestrial	0.78	0.71	1.214	519	2011
Kepler-42 d	Rocky Terrestrial	0.57	0.36	1.865	450	2011

Kepler-42 c Planet Profile

Physical Specs

Radius

0.73 R⊕

Radius (Jupiter)

0.065 R♃

Mass

60.34 M⊕

Mass (Jupiter)

0.190 M♃

Density

98.00 g/cm³

Surface Gravity

113.22 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.185

HZ Position Inner

Controversial No

Discovery

Year 2011

Method Transit

Facility Kepler

Telescope 0.95 m Kepler Telescope

Size rank in cohort

Rank by radius

#518of 570

top 90.7%

This planet

0.73R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-124 b 0.73 R⊕ Kepler-1371 b 0.73 R⊕ Kepler-1967 b 0.73 R⊕

Metric	Earth	Kepler-42 c	Jupiter
Radius (R⊕)	1.00	0.73	11.21
Mass (M⊕)	1.00	60.34	317.83
Density (g/cm³)	5.51	98.00	1.33
Surface Gravity (g)	1.00	113.22	2.53
Insolation (S⊕)	1.00	82.13	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	60.337 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 63126862

Gaia DR2

Gaia DR2 2126556132093765888

Gaia DR3

Gaia DR3 2126556132093765888

System

Kepler-42

Percentile among Rocky Terrestrial cohort

Radius 0.730 R⊕ · percentile 9 / cohort 570

Mass 60.337 M⊕ · percentile 99 / cohort 570

Orbital period 0.45 d · percentile 2 / cohort 567

Distance 40.06 pc · percentile 17 / cohort 566

ESI 0.185 · percentile 12 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

0.453 days

Semi-major axis

0.0060 AU

Eccentricity

0.000

Inclination

81.11 °

Year Length

A year here lasts roughly 10.9 hours long on a nearly circular orbit at a mean orbital distance of 0.0060 AU.

Transit Fingerprint

Depth

0.156 %

Duration

0.445 h

Impact parameter b

0.520

Rp / R★

0.039500

Transit midpoint (BJD)

2,454,966.8695

Photometric dip

Transit produces a flux drop of 1,560 ppm lasting ≈ 0.44 h.

Extended Orbital Architecture

Planet / star radius ratio

0.039500

Semi-major axis / stellar radius

4.440

Impact parameter (b)

0.520

Transit mid-time (BJD)

2,454,966.8695

Angular separation (arcsec)

0.15000

Eq. Temperature

720K

(447 °C)

Insolation (S⊕)

82.13

Earth = 1.00

Earth Similarity (ESI)

0.185

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

Muirhead et al. 2012

Instrument

Kepler CCD Array

Publication

2012-03

Observation locale

Space

Discovery cohort

Planets confirmed in 2011 at Kepler (12 shown).

Kepler-22 b · Sub-Neptune Kepler-20 d · Sub-Neptune Kepler-26 c · Sub-Neptune Kepler-19 c · Sub-Neptune Kepler-26 b · Sub-Neptune Kepler-28 c · Super-Earth Kepler-10 c · Sub-Neptune Kepler-20 f · Rocky Terrestrial Kepler-42 d · Rocky Terrestrial Kepler-16 b · Neptune-like Kepler-28 b · Super-Earth Kepler-34 b · Neptune-like

Host System: Kepler-42

Spectral Class

M-type red dwarf

Effective Temperature

3,068 K — cooler than the Sun (5,778 K)

Estimated Age

4.50 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.170 R☉

Stellar Mass

0.130 M☉

Metallicity [Fe/H]

-0.33

Extended Stellar Properties

Surface gravity (log g)

5.110 dex

Stellar density

26.800 g/cm³

Systemic radial velocity

-84.48 km/s

Rotational v·sin i

3.30 km/s

Metallicity ratio

[M/H]

Distance

40.06 parsec

Light-years 130.66 ly

V-band magnitude

16.70 mag

Voyager-speed travel 2,304,127 yr

Multi-band Host Photometry — 15 bands

Astrometric Data

Parallax

24.934 mas

Total Proper Motion

427.682 mas/yr

PM Right Ascension

93.13 mas/yr

PM Declination

-417.42 mas/yr

Galactic Cartesian (pc)

x = 0.269 · y = -0.659 · z = 0.702

Equatorial (J2000)

RA 292.21960° · Dec 44.61737°

Galactic ℓ, b

76.917° · 12.547°

Ecliptic λ, β

309.612° · 65.030°

HTM-20 index

-797492186