Key parameters at a glance
- A radius of 2.76 Earth radii
- A mass of 8.05 Earth masses
- Surface gravity around 1.06 g
- An orbital period of 30.952 days
- Semi-major axis 0.1649 AU
- Equilibrium temperature 338 K (65 °C)
- Distance from Earth 526.92 light-years
- Earth Similarity Index 0.658
- Travel time at Voyager 1 speed 9,292,257 years
- Almost certainly tidally locked to its host star given the close orbit
K2-123 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#794of 1978
top 40.1%
This planet
2.76R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-123 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.76 | 11.21 |
| Mass (M⊕) | 1.00 | 8.05 | 317.83 |
| Density (g/cm³) | 5.51 | 2.10 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.06 | 2.53 |
| Insolation (S⊕) | 1.00 | 2.90 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 197249801
Gaia DR2
Gaia DR2 685065155072248192
Gaia DR3
Gaia DR3 685065155072248192
System
K2-123
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 30.95 Earth days (8.5% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1649 AU.
Transit Fingerprint
Depth
0.212 %
Duration
3.761 h
Impact parameter b
0.390
Rp / R★
0.042700
Transit midpoint (BJD)
2,457,147.4973
Photometric dip
Transit produces a flux drop of 2,117 ppm lasting ≈ 3.76 h.
Extended Orbital Architecture
Planet / star radius ratio
0.042700
Semi-major axis / stellar radius
61.210
Impact parameter (b)
0.390
Transit mid-time (BJD)
2,457,147.4973
Long. of periastron (ω)
-33.53°
Angular separation (arcsec)
1.02000
Eq. Temperature
338K
(65 °C)
Insolation (S⊕)
2.90
Earth = 1.00
Earth Similarity (ESI)
0.658
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — liquid water is physically possible with adequate atmospheric pressure. 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: K2-123
Spectral Class
K-type orange
Effective Temperature
4,035 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.590 R☉
Stellar Mass
0.620 M☉
Metallicity [Fe/H]
0.03
Extended Stellar Properties
Surface gravity (log g)
4.690 dex
Stellar density
4.511 g/cm³
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 12 bands
Astrometric Data
Parallax
6.161 mas
Total Proper Motion
59.978 mas/yr
PM Right Ascension
-11.48 mas/yr
PM Declination
-58.87 mas/yr
Galactic Cartesian (pc)
x = -0.652 · y = 0.664 · z = 0.366
Equatorial (J2000)
RA 134.44414° · Dec 21.45327°
Galactic ℓ, b
205.514° · 36.914°
Ecliptic λ, β
130.792° · 4.086°
HTM-20 index
-353666672
Similar Worlds
TOI-1260 c
Sub-Neptune · K-type orange
Radius 2.76 R⊕ · 240.0 ly
Kepler-305 d
Sub-Neptune · K-type orange
Radius 2.76 R⊕ · 2,832.6 ly
TOI-125 c
Sub-Neptune · K-type orange
Radius 2.76 R⊕ · 362.2 ly
TOI-969 b
Sub-Neptune · K-type orange
Radius 2.77 R⊕ · 252.0 ly
TOI-444 b
Sub-Neptune · K-type orange
Radius 2.77 R⊕ · 187.2 ly
Kepler-304 d
Sub-Neptune · K-type orange
Radius 2.75 R⊕ · 1,417.7 ly