Key parameters at a glance
- A radius of 3.96 Earth radii
- A mass of 56.00 Earth masses
- Surface gravity around 3.58 g
- An orbital period of 30.156 days
- Semi-major axis 0.2020 AU
- Equilibrium temperature 586 K (313 °C)
- Distance from Earth 1,444.97 light-years
- Earth Similarity Index 0.416
- Travel time at Voyager 1 speed 25,482,026 years
- Almost certainly tidally locked to its host star given the close orbit
1 sibling around Kepler-278
Kepler-278 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 |
|---|---|---|---|---|---|---|
| Kepler-278 b this | Sub-Neptune | 3.96 | 56.00 | 30.156 | 586 | 2014 |
| Kepler-278 c | Sub-Neptune | 3.27 | 34.90 | 51.111 | 492 | 2014 |
Kepler-278 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#7of 1978
top 0.3%
This planet
3.96R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | Kepler-278 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 3.96 | 11.21 |
| Mass (M⊕) | 1.00 | 56.00 | 317.83 |
| Density (g/cm³) | 5.51 | 5.00 | 1.33 |
| Surface Gravity (g) | 1.00 | 3.58 | 2.53 |
| Insolation (S⊕) | 1.00 | 110.00 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 56.000 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 122225232
Gaia DR2
Gaia DR2 2052881912366613376
Gaia DR3
Gaia DR3 2052881912366613376
System
Kepler-278
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 30.16 Earth days (8.3% of a terrestrial year) on a highly eccentric trajectory at a mean orbital distance of 0.2020 AU.
Transit Fingerprint
Depth
0.018 %
Duration
7.874 h
Impact parameter b
0.544
Rp / R★
0.012660
Transit midpoint (BJD)
2,455,695.3727
Photometric dip
Transit produces a flux drop of 176 ppm lasting ≈ 7.87 h.
Extended Orbital Architecture
Planet / star radius ratio
0.012660
Semi-major axis / stellar radius
15.152
Impact parameter (b)
0.544
RV semi-amplitude (K)
14.000 m/s
Transit mid-time (BJD)
2,455,695.3727
Long. of periastron (ω)
21.10°
Angular separation (arcsec)
0.45600
Eq. Temperature
586K
(313 °C)
Insolation (S⊕)
110.00
Earth = 1.00
Earth Similarity (ESI)
0.416
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.
Detection Signatures
Transit photometry
A transit dip has been observed from at least one telescope.
Radial velocity
Stellar wobble has been measured spectroscopically.
Transit timing variations
Gravitational interactions from neighbours have been detected.
Discovery Paper
Primary reference
Rowe et al. 2014Instrument
Kepler CCD Array
Publication
2014-03
Observation locale
Space
Discovery cohort
Planets confirmed in 2014 at Kepler (12 shown).
Host System: Kepler-278
Spectral Class
K-type orange
Effective Temperature
4,965 K — cooler than the Sun (5,778 K)
Estimated Age
5.76 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
2.861 R☉
Stellar Mass
1.227 M☉
Metallicity [Fe/H]
0.22
Extended Stellar Properties
Surface gravity (log g)
3.580 dex
Stellar density
0.072 g/cm³
Systemic radial velocity
-46.98 km/s
Rotational v·sin i
2.50 km/s
Activity index (log R'HK)
-5.310
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 17 bands
Astrometric Data
Parallax
2.229 mas
Total Proper Motion
9.331 mas/yr
PM Right Ascension
2.64 mas/yr
PM Declination
8.95 mas/yr
Galactic Cartesian (pc)
x = 0.268 · y = -0.733 · z = 0.625
Equatorial (J2000)
RA 290.10721° · Dec 38.70227°
Galactic ℓ, b
70.772° · 11.390°
Ecliptic λ, β
302.341° · 59.904°
HTM-20 index
1745041340
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