Key parameters at a glance
- A radius of 1.21 Earth radii
- A mass of 1.92 Earth masses
- Surface gravity around 1.31 g
- An orbital period of 20.838 days
- Semi-major axis 0.1280 AU
- Equilibrium temperature 418 K (145 °C)
- Distance from Earth 1,135.97 light-years
- Earth Similarity Index 0.719
- Travel time at Voyager 1 speed 20,032,865 years
- Almost certainly tidally locked to its host star given the close orbit
2 siblings around Kepler-81
Kepler-81 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-81 b | Sub-Neptune | 2.42 | 17.20 | 5.955 | 635 | 2012 |
| Kepler-81 c | Sub-Neptune | 2.37 | 4.30 | 12.040 | 502 | 2012 |
| Kepler-81 d this | Rocky Terrestrial | 1.21 | 1.92 | 20.838 | 418 | 2014 |
Kepler-81 d Planet Profile
Physical Specs
Classification
Planet Type
Rocky Terrestrial
Discovery
Size rank in cohort
Rank by radius
#56of 570
top 9.6%
This planet
1.21R⊕
Rocky Terrestrial median
1.01R⊕
Nearest-size peers
| Metric | Earth | Kepler-81 d | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 1.21 | 11.21 |
| Mass (M⊕) | 1.00 | 1.92 | 317.83 |
| Density (g/cm³) | 5.51 | 5.96 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.31 | 2.53 |
| Insolation (S⊕) | 1.00 | 7.51 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 270611154
Gaia DR2
Gaia DR2 2077816087307845248
Gaia DR3
Gaia DR3 2077816087307845248
System
Kepler-81
Percentile among Rocky Terrestrial cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 20.84 Earth days (5.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1280 AU.
Transit Fingerprint
Depth
0.040 %
Duration
2.570 h
Impact parameter b
0.710
Rp / R★
0.017962
Transit midpoint (BJD)
2,454,965.0796
Photometric dip
Transit produces a flux drop of 398 ppm lasting ≈ 2.57 h.
Extended Orbital Architecture
Planet / star radius ratio
0.017962
Semi-major axis / stellar radius
26.900
Impact parameter (b)
0.710
Transit mid-time (BJD)
2,454,965.0796
Angular separation (arcsec)
0.36800
Eq. Temperature
418K
(145 °C)
Insolation (S⊕)
7.51
Earth = 1.00
Earth Similarity (ESI)
0.719
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
Rowe et al. 2014Instrument
Kepler CCD Array
Publication
2014-03
Observation locale
Space
Discovery cohort
Planets confirmed in 2014 at Kepler (12 shown).
Host System: Kepler-81
Spectral Class
M-type red dwarf
Effective Temperature
4,500 K — cooler than the Sun (5,778 K)
Estimated Age
3.63 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.595 R☉
Stellar Mass
0.648 M☉
Metallicity [Fe/H]
-0.18
Extended Stellar Properties
Surface gravity (log g)
4.696 dex
Stellar density
4.193 g/cm³
Metallicity ratio
[M/H]
Multi-band Host Photometry — 16 bands
Astrometric Data
Parallax
2.843 mas
Total Proper Motion
24.701 mas/yr
PM Right Ascension
-1.37 mas/yr
PM Declination
-24.66 mas/yr
Galactic Cartesian (pc)
x = 0.294 · y = -0.672 · z = 0.680
Equatorial (J2000)
RA 293.63694° · Dec 42.82483°
Galactic ℓ, b
75.746° · 10.830°
Ecliptic λ, β
310.352° · 62.991°
HTM-20 index
-84634903
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