Key parameters at a glance
- A radius of 3.58 Earth radii
- A mass of 12.50 Earth masses
- Surface gravity around 0.98 g
- An orbital period of 10.352 days
- Semi-major axis 0.0856 AU
- Equilibrium temperature 631 K (358 °C)
- Distance from Earth 1,316.08 light-years
- Earth Similarity Index 0.346
- Travel time at Voyager 1 speed 23,209,102 years
- Almost certainly tidally locked to its host star given the close orbit
1 sibling around K2-8
K2-8 b 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 |
|---|---|---|---|---|---|---|
| K2-8 c | Sub-Neptune | 2.41 | 6.39 | 5.064 | 801 | 2016 |
| K2-8 b this | Sub-Neptune | 3.58 | 12.50 | 10.352 | 631 | 2015 |
K2-8 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#144of 1978
top 7.2%
This planet
3.58R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-8 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 3.58 | 11.21 |
| Mass (M⊕) | 1.00 | 12.50 | 317.83 |
| Density (g/cm³) | 5.51 | 1.50 | 1.33 |
| Surface Gravity (g) | 1.00 | 0.98 | 2.53 |
| Insolation (S⊕) | 1.00 | 37.70 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 38114658
Gaia DR2
Gaia DR2 3797977118144236288
Gaia DR3
Gaia DR3 3797977118144236288
System
K2-8
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 10.35 Earth days (2.8% of a terrestrial year) at a mean orbital distance of 0.0856 AU.
Transit Fingerprint
Depth
0.147 %
Duration
3.362 h
Impact parameter b
0.880
Rp / R★
0.044570
Transit midpoint (BJD)
2,456,813.6114
Photometric dip
Transit produces a flux drop of 1,470 ppm lasting ≈ 3.36 h.
Extended Orbital Architecture
Planet / star radius ratio
0.044570
Semi-major axis / stellar radius
14.100
Impact parameter (b)
0.880
Transit mid-time (BJD)
2,456,813.6114
Angular separation (arcsec)
0.21200
Eq. Temperature
631K
(358 °C)
Insolation (S⊕)
37.70
Earth = 1.00
Earth Similarity (ESI)
0.346
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water. Close-orbiting tidally-locked around a cool host.
Discovery Paper
Primary reference
Montet et al. 2015Instrument
Kepler CCD Array
Publication
2015-08
Observation locale
Space
Discovery cohort
Planets confirmed in 2015 at K2 (12 shown).
Host System: K2-8
Spectral Class
K-type orange
Effective Temperature
4,870 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.740 R☉
Stellar Mass
0.780 M☉
Metallicity [Fe/H]
-0.02
Extended Stellar Properties
Surface gravity (log g)
4.520 dex
Stellar density
2.363 g/cm³
Rotational v·sin i
2.00 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 17 bands
Astrometric Data
Parallax
2.451 mas
Total Proper Motion
39.384 mas/yr
PM Right Ascension
-36.02 mas/yr
PM Declination
-15.92 mas/yr
Galactic Cartesian (pc)
x = -0.984 · y = 0.177 · z = -0.005
Equatorial (J2000)
RA 169.79352° · Dec -0.28444°
Galactic ℓ, b
260.189° · 54.742°
Ecliptic λ, β
170.728° · -4.303°
HTM-20 index
155680486
Similar Worlds
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KOBE-1 c
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Kepler-305 b
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Kepler-258 c
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HIP 35173 b
Sub-Neptune · K-type orange
Radius 3.61 R⊕ · 108.1 ly