Key parameters at a glance
- A radius of 2.29 Earth radii
- A mass of 8.30 Earth masses
- Surface gravity around 1.58 g
- An orbital period of 10.561 days
- Semi-major axis 0.0951 AU
- Equilibrium temperature 916 K (643 °C)
- Distance from Earth 628.47 light-years
- Earth Similarity Index 0.296
- Travel time at Voyager 1 speed 11,083,068 years
1 sibling around K2-38
K2-38 c 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 |
|---|---|---|---|---|---|---|
| K2-38 b | Super-Earth | 1.54 | 7.30 | 4.016 | 1,266 | 2016 |
| K2-38 c this | Sub-Neptune | 2.29 | 8.30 | 10.561 | 916 | 2016 |
K2-38 c Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1519of 1978
top 76.7%
This planet
2.29R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-38 c | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.29 | 11.21 |
| Mass (M⊕) | 1.00 | 8.30 | 317.83 |
| Density (g/cm³) | 5.51 | 3.80 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.58 | 2.53 |
| Insolation (S⊕) | 1.00 | 117.00 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 8.300 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 12666215
Gaia DR2
Gaia DR2 6237129658760381056
Gaia DR3
Gaia DR3 6237129658760381056
System
K2-38
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 10.56 Earth days (2.9% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0951 AU.
Transit Fingerprint
Depth
0.048 %
Duration
2.380 h
Impact parameter b
0.640
Rp / R★
0.020000
Transit midpoint (BJD)
2,456,900.4752
Photometric dip
Transit produces a flux drop of 484 ppm lasting ≈ 2.38 h.
Extended Orbital Architecture
Planet / star radius ratio
0.020000
Semi-major axis / stellar radius
19.300
Impact parameter (b)
0.640
RV semi-amplitude (K)
2.410 m/s
Transit mid-time (BJD)
2,456,900.4752
Long. of periastron (ω)
153.00°
Angular separation (arcsec)
0.49400
Eq. Temperature
916K
(643 °C)
Insolation (S⊕)
117.00
Earth = 1.00
Earth Similarity (ESI)
0.296
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.
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
Sinukoff et al. 2016Instrument
Kepler CCD Array
Publication
2016-08
Observation locale
Space
Discovery cohort
Planets confirmed in 2016 at K2 (12 shown).
Host System: K2-38
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
5,731 K — cooler than the Sun (5,778 K)
Estimated Age
6.70 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
1.060 R☉
Stellar Mass
1.030 M☉
Metallicity [Fe/H]
0.26
Extended Stellar Properties
Surface gravity (log g)
4.380 dex
Stellar density
1.210 g/cm³
Systemic radial velocity
-35.33 km/s
Rotational v·sin i
2.00 km/s
Activity index (log R'HK)
-5.060
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 12 bands
Astrometric Data
Parallax
5.162 mas
Total Proper Motion
68.273 mas/yr
PM Right Ascension
-56.97 mas/yr
PM Declination
-37.63 mas/yr
Galactic Cartesian (pc)
x = -0.459 · y = -0.796 · z = -0.394
Equatorial (J2000)
RA 240.03331° · Dec -23.18942°
Galactic ℓ, b
349.629° · 22.121°
Ecliptic λ, β
242.635° · -2.552°
HTM-20 index
682796070
Similar Worlds
K2-356 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.29 R⊕ · 1,159.6 ly
Kepler-626 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.29 R⊕ · 2,073.2 ly
Kepler-319 d
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.29 R⊕ · 1,642.0 ly
Kepler-1374 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.29 R⊕ · 3,517.5 ly
Kepler-1334 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.29 R⊕ · 3,989.0 ly
HD 35843 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.29 R⊕ · 227.0 ly