Key parameters at a glance
- A radius of 2.03 Earth radii
- A mass of 7.00 Earth masses
- Surface gravity around 1.70 g
- An orbital period of 8.327 days
- Semi-major axis 0.0769 AU
- Equilibrium temperature 750 K (477 °C)
- Distance from Earth 334.52 light-years
- Earth Similarity Index 0.385
- Travel time at Voyager 1 speed 5,899,236 years
1 sibling around K2-229
K2-229 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 |
|---|---|---|---|---|---|---|
| K2-229 b | Rocky Terrestrial | 1.00 | 2.55 | 0.584 | 1,818 | 2018 |
| K2-229 c this | Sub-Neptune | 2.03 | 7.00 | 8.327 | 750 | 2018 |
K2-229 c 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 | K2-229 c | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.03 | 11.21 |
| Mass (M⊕) | 1.00 | 7.00 | 317.83 |
| Density (g/cm³) | 5.51 | 5.10 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.70 | 2.53 |
| Insolation (S⊕) | 1.00 | 66.00 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 7.000 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 98720809
Gaia DR2
Gaia DR2 3583630929786305280
Gaia DR3
Gaia DR3 3583630934082556416
System
K2-229
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 8.33 Earth days (2.3% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0769 AU.
Transit Fingerprint
Depth
0.053 %
Duration
2.500 h
Impact parameter b
0.390
Rp / R★
0.023600
Transit midpoint (BJD)
2,457,586.3431
Photometric dip
Transit produces a flux drop of 533 ppm lasting ≈ 2.50 h.
Extended Orbital Architecture
Planet / star radius ratio
0.023600
Semi-major axis / stellar radius
24.900
Impact parameter (b)
0.390
Transit mid-time (BJD)
2,457,586.3431
Angular separation (arcsec)
0.75000
Eq. Temperature
750K
(477 °C)
Insolation (S⊕)
66.00
Earth = 1.00
Earth Similarity (ESI)
0.385
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
Mayo et al. 2018Instrument
Kepler CCD Array
Publication
2018-03
Observation locale
Space
Discovery cohort
Planets confirmed in 2018 at K2 (12 shown).
Host System: K2-229
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
5,315 K — cooler than the Sun (5,778 K)
Estimated Age
5.40 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.790 R☉
Stellar Mass
0.870 M☉
Metallicity [Fe/H]
-0.09
Extended Stellar Properties
Surface gravity (log g)
4.590 dex
Stellar density
2.380 g/cm³
Rotational v·sin i
2.46 km/s
Rotation period
18.10 days
Activity index (log R'HK)
-4.603
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 12 bands
Astrometric Data
Parallax
9.723 mas
Total Proper Motion
81.227 mas/yr
PM Right Ascension
-80.89 mas/yr
PM Declination
7.43 mas/yr
Galactic Cartesian (pc)
x = -0.986 · y = -0.119 · z = -0.117
Equatorial (J2000)
RA 186.87292° · Dec -6.72185°
Galactic ℓ, b
292.352° · 55.657°
Ecliptic λ, β
188.964° · -3.447°
HTM-20 index
827102690
Similar Worlds
GJ 2030 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.03 R⊕ · 120.9 ly
Kepler-761 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.03 R⊕ · 2,709.4 ly
K2-84 c
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.03 R⊕ · 929.1 ly
K2-342 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.03 R⊕ · 679.6 ly
Kepler-1268 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.03 R⊕ · 6,003.8 ly
Kepler-195 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.03 R⊕ · 2,126.7 ly