Key parameters at a glance
- A radius of 2.20 Earth radii
- A mass of 6.86 Earth masses
- Surface gravity around 1.42 g
- An orbital period of 11.600 days
- Semi-major axis 0.0959 AU
- Equilibrium temperature 671 K (398 °C)
- Distance from Earth 2,100.90 light-years
- Earth Similarity Index 0.406
- Travel time at Voyager 1 speed 37,049,392 years
- Almost certainly tidally locked to its host star given the close orbit
1 sibling around Kepler-57
Kepler-57 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 |
|---|---|---|---|---|---|---|
| Kepler-57 b | Sub-Neptune | 3.14 | 25.06 | 5.720 | 850 | 2012 |
| Kepler-57 c this | Sub-Neptune | 2.20 | 6.86 | 11.600 | 671 | 2012 |
Kepler-57 c Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1689of 1978
top 85.3%
This planet
2.20R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | Kepler-57 c | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.20 | 11.21 |
| Mass (M⊕) | 1.00 | 6.86 | 317.83 |
| Density (g/cm³) | 5.51 | 3.53 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.42 | 2.53 |
| Insolation (S⊕) | 1.00 | 48.57 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 6.860 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 270615136
Gaia DR2
Gaia DR2 2126418658780855296
Gaia DR3
Gaia DR3 2126418658780855296
System
Kepler-57
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 11.60 Earth days (3.2% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0959 AU.
Transit Fingerprint
Depth
0.049 %
Duration
2.260 h
Impact parameter b
0.030
Rp / R★
0.019868
Transit midpoint (BJD)
2,454,966.9932
Photometric dip
Transit produces a flux drop of 489 ppm lasting ≈ 2.26 h.
Extended Orbital Architecture
Planet / star radius ratio
0.019868
Semi-major axis / stellar radius
8.180
Impact parameter (b)
0.030
Transit mid-time (BJD)
2,454,966.9932
Angular separation (arcsec)
0.14900
Eq. Temperature
671K
(398 °C)
Insolation (S⊕)
48.57
Earth = 1.00
Earth Similarity (ESI)
0.406
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.
Transit timing variations
Gravitational interactions from neighbours have been detected.
Discovery Paper
Primary reference
Steffen et al. 2013Instrument
Kepler CCD Array
Publication
2013-01
Observation locale
Space
Discovery cohort
Planets confirmed in 2012 at Kepler (12 shown).
Host System: Kepler-57
Spectral Class
K-type orange
Effective Temperature
5,188 K — cooler than the Sun (5,778 K)
Estimated Age
3.31 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.826 R☉
Stellar Mass
0.859 M☉
Metallicity [Fe/H]
0.12
Extended Stellar Properties
Surface gravity (log g)
4.540 dex
Stellar density
2.129 g/cm³
Metallicity ratio
[M/H]
Multi-band Host Photometry — 16 bands
Astrometric Data
Parallax
1.524 mas
Total Proper Motion
7.221 mas/yr
PM Right Ascension
4.16 mas/yr
PM Declination
5.90 mas/yr
Galactic Cartesian (pc)
x = 0.285 · y = -0.652 · z = 0.703
Equatorial (J2000)
RA 293.64131° · Dec 44.65707°
Galactic ℓ, b
77.413° · 11.658°
Ecliptic λ, β
311.864° · 64.698°
HTM-20 index
-1626224670
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Kepler-229 b
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Kepler-240 c
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Kepler-1378 b
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HD 110067 b
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