Key parameters at a glance
- A radius of 2.90 Earth radii
- A mass of 8.75 Earth masses
- Surface gravity around 1.04 g
- An orbital period of 1.964 days
- Semi-major axis 0.0274 AU
- Equilibrium temperature 1,034 K (761 °C)
- Distance from Earth 624.94 light-years
- Earth Similarity Index 0.228
- Travel time at Voyager 1 speed 11,020,834 years
- Almost certainly tidally locked to its host star given the close orbit
K2-255 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#621of 1978
top 31.3%
This planet
2.90R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-255 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.90 | 11.21 |
| Mass (M⊕) | 1.00 | 8.75 | 317.83 |
| Density (g/cm³) | 5.51 | 1.97 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.04 | 2.53 |
| Insolation (S⊕) | 1.00 | — | 0.037 |
Star Catalogue Identifiers
TIC
TIC 51664268
Gaia DR2
Gaia DR2 3682825883842696832
Gaia DR3
Gaia DR3 3682825883842696832
System
K2-255
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 1.96 Earth days (0.5% of a terrestrial year) at a mean orbital distance of 0.0274 AU.
Transit Fingerprint
Depth
0.183 %
Duration
1.100 h
Impact parameter b
0.440
Rp / R★
0.038600
Transit midpoint (BJD)
2,457,583.3015
Photometric dip
Transit produces a flux drop of 1,830 ppm lasting ≈ 1.10 h.
Extended Orbital Architecture
Planet / star radius ratio
0.038600
Semi-major axis / stellar radius
9.100
Impact parameter (b)
0.440
Transit mid-time (BJD)
2,457,583.3015
Angular separation (arcsec)
0.14300
Eq. Temperature
1,034K
(761 °C)
Insolation (S⊕)
—
Earth = 1.00
Earth Similarity (ESI)
0.228
0 = alien, 1 = Earth-identical
Insufficient insolation data — the dayside is scorched. Close-orbiting tidally-locked around a cool host.
Discovery Paper
Primary reference
Livingston et al. 2018Instrument
Kepler CCD Array
Publication
2018-08
Observation locale
Space
Discovery cohort
Planets confirmed in 2018 at K2 (12 shown).
Host System: K2-255
Spectral Class
K-type orange
Effective Temperature
4,676 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.690 R☉
Stellar Mass
0.710 M☉
Metallicity [Fe/H]
-0.14
Extended Stellar Properties
Surface gravity (log g)
4.620 dex
Stellar density
1.948 g/cm³
Rotational v·sin i
2.46 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 17 bands
Astrometric Data
Parallax
5.191 mas
Total Proper Motion
29.839 mas/yr
PM Right Ascension
-29.56 mas/yr
PM Declination
-4.08 mas/yr
Galactic Cartesian (pc)
x = -0.983 · y = -0.172 · z = -0.059
Equatorial (J2000)
RA 189.91285° · Dec -3.37056°
Galactic ℓ, b
297.151° · 59.369°
Ecliptic λ, β
190.429° · 0.826°
HTM-20 index
-228412260
Similar Worlds
Kepler-716 b
Sub-Neptune · K-type orange
Radius 2.90 R⊕ · 2,071.1 ly
KOBE-1 b
Sub-Neptune · K-type orange
Radius 2.91 R⊕ · 78.2 ly
Kepler-781 b
Sub-Neptune · K-type orange
Radius 2.89 R⊕ · 3,471.8 ly
Kepler-391 c
Sub-Neptune · K-type orange
Radius 2.88 R⊕ · 2,835.1 ly
K2-378 b
Sub-Neptune · K-type orange
Radius 2.88 R⊕ · 2,243.9 ly
Kepler-709 b
Sub-Neptune · K-type orange
Radius 2.92 R⊕ · 2,168.4 ly