Key parameters at a glance
- A radius of 2.31 Earth radii
- A mass of 5.95 Earth masses
- Surface gravity around 1.12 g
- An orbital period of 6.679 days
- Semi-major axis 0.0680 AU
- Equilibrium temperature 877 K (604 °C)
- Distance from Earth 789.67 light-years
- Earth Similarity Index 0.296
- Travel time at Voyager 1 speed 13,925,760 years
1 sibling around K2-189
K2-189 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 |
|---|---|---|---|---|---|---|
| K2-189 b | Super-Earth | 1.40 | 2.55 | 2.588 | 1,203 | 2018 |
| K2-189 c this | Sub-Neptune | 2.31 | 5.95 | 6.679 | 877 | 2018 |
K2-189 c Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1486of 1978
top 75.1%
This planet
2.31R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-189 c | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.31 | 11.21 |
| Mass (M⊕) | 1.00 | 5.95 | 317.83 |
| Density (g/cm³) | 5.51 | 2.65 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.12 | 2.53 |
| Insolation (S⊕) | 1.00 | 140.00 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 422349881
Gaia DR2
Gaia DR2 3606343094804432128
Gaia DR3
Gaia DR3 3606343094804432128
System
K2-189
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 6.68 Earth days (1.8% of a terrestrial year) at a mean orbital distance of 0.0680 AU.
Transit Fingerprint
Depth
0.078 %
Duration
2.710 h
Impact parameter b
0.370
Rp / R★
0.026200
Transit midpoint (BJD)
2,457,223.4182
Photometric dip
Transit produces a flux drop of 784 ppm lasting ≈ 2.71 h.
Extended Orbital Architecture
Planet / star radius ratio
0.026200
Semi-major axis / stellar radius
18.170
Impact parameter (b)
0.370
Transit mid-time (BJD)
2,457,223.4182
Angular separation (arcsec)
0.28100
Eq. Temperature
877K
(604 °C)
Insolation (S⊕)
140.00
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.
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: K2-189
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
5,442 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.879 R☉
Stellar Mass
0.850 M☉
Metallicity [Fe/H]
-0.10
Extended Stellar Properties
Surface gravity (log g)
4.510 dex
Stellar density
2.072 g/cm³
Systemic radial velocity
15.96 km/s
Rotational v·sin i
1.90 km/s
Activity index (log R'HK)
-4.999
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 12 bands
Astrometric Data
Parallax
4.102 mas
Total Proper Motion
60.231 mas/yr
PM Right Ascension
28.42 mas/yr
PM Declination
-53.10 mas/yr
Galactic Cartesian (pc)
x = -0.885 · y = -0.387 · z = -0.259
Equatorial (J2000)
RA 203.62144° · Dec -15.03652°
Galactic ℓ, b
318.137° · 46.560°
Ecliptic λ, β
207.375° · -4.824°
HTM-20 index
678412323
Similar Worlds
K2-37 d
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.31 R⊕ · 586.9 ly
Kepler-926 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.31 R⊕ · 3,005.1 ly
Kepler-981 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.31 R⊕ · 2,863.9 ly
Kepler-244 d
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.31 R⊕ · 3,380.6 ly
Kepler-1926 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.31 R⊕ · 2,176.8 ly
TOI-1443 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.30 R⊕ · 279.9 ly