Key parameters at a glance
- A radius of 2.03 Earth radii
- A mass of 4.78 Earth masses
- Surface gravity around 1.16 g
- An orbital period of 1.292 days
- Semi-major axis 0.0189 AU
- Equilibrium temperature 868 K (595 °C)
- Distance from Earth 331.48 light-years
- Earth Similarity Index 0.314
- Travel time at Voyager 1 speed 5,845,629 years
- Almost certainly tidally locked to its host star given the close orbit
1 sibling around K2-117
K2-117 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 |
|---|---|---|---|---|---|---|
| K2-117 b this | Sub-Neptune | 2.03 | 4.78 | 1.292 | 868 | 2017 |
| K2-117 c | Sub-Neptune | 2.06 | 4.90 | 5.444 | 537 | 2017 |
K2-117 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1915of 1978
top 96.8%
This planet
2.03R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-117 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.03 | 11.21 |
| Mass (M⊕) | 1.00 | 4.78 | 317.83 |
| Density (g/cm³) | 5.51 | 3.14 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.16 | 2.53 |
| Insolation (S⊕) | 1.00 | 145.80 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 458686847
Gaia DR2
Gaia DR2 597829077890316928
Gaia DR3
Gaia DR3 597829077890316928
System
K2-117
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 1.29 Earth days (0.4% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0189 AU.
Transit Fingerprint
Depth
0.182 %
Duration
1.152 h
Impact parameter b
0.390
Rp / R★
0.036300
Transit midpoint (BJD)
2,457,142.7745
Photometric dip
Transit produces a flux drop of 1,817 ppm lasting ≈ 1.15 h.
Extended Orbital Architecture
Planet / star radius ratio
0.036300
Semi-major axis / stellar radius
7.870
Impact parameter (b)
0.390
Transit mid-time (BJD)
2,457,142.7745
Long. of periastron (ω)
-22.63°
Angular separation (arcsec)
0.18600
Eq. Temperature
868K
(595 °C)
Insolation (S⊕)
145.80
Earth = 1.00
Earth Similarity (ESI)
0.314
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
Dressing et al. 2017Instrument
Kepler CCD Array
Publication
2017-11
Observation locale
Space
Discovery cohort
Planets confirmed in 2017 at K2 (12 shown).
Host System: K2-117
Spectral Class
M-type red dwarf
Effective Temperature
3,778 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.510 R☉
Stellar Mass
0.540 M☉
Metallicity [Fe/H]
-0.05
Extended Stellar Properties
Surface gravity (log g)
4.750 dex
Stellar density
5.297 g/cm³
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 17 bands
Astrometric Data
Parallax
9.811 mas
Total Proper Motion
21.435 mas/yr
PM Right Ascension
11.55 mas/yr
PM Declination
18.06 mas/yr
Galactic Cartesian (pc)
x = -0.681 · y = 0.709 · z = 0.182
Equatorial (J2000)
RA 133.85573° · Dec 10.46922°
Galactic ℓ, b
217.625° · 32.246°
Ecliptic λ, β
133.302° · -6.623°
HTM-20 index
415865403
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