Key parameters at a glance
- A radius of 2.61 Earth radii
- A mass of 7.32 Earth masses
- Surface gravity around 1.07 g
- An orbital period of 2.383 days
- Semi-major axis 0.0340 AU
- Equilibrium temperature 1,237 K (964 °C)
- Distance from Earth 2,544.85 light-years
- Earth Similarity Index 0.194
- Travel time at Voyager 1 speed 44,878,458 years
- Almost certainly tidally locked to its host star given the close orbit
2 siblings around Kepler-257
Kepler-257 b shares its host star with 2 other confirmed planets. Side-by-side measurements below.
| Planet | Type | Radius (R⊕) | Mass (M⊕) | Period (d) | Eq. T (K) | Year |
|---|---|---|---|---|---|---|
| Kepler-257 b this | Sub-Neptune | 2.61 | 7.32 | 2.383 | 1,237 | 2014 |
| Kepler-257 c | Neptune-like | 5.41 | 25.20 | 6.581 | 881 | 2014 |
| Kepler-257 d | Neptune-like | 4.95 | 21.70 | 24.665 | 567 | 2014 |
Kepler-257 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#999of 1978
top 50.5%
This planet
2.61R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | Kepler-257 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.61 | 11.21 |
| Mass (M⊕) | 1.00 | 7.32 | 317.83 |
| Density (g/cm³) | 5.51 | 2.26 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.07 | 2.53 |
| Insolation (S⊕) | 1.00 | 343.60 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 273132699
Gaia DR2
Gaia DR2 2080246282881778048
Gaia DR3
Gaia DR3 2080246282881778048
System
Kepler-257
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 2.38 Earth days (0.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0340 AU.
Transit Fingerprint
Depth
0.079 %
Duration
1.812 h
Impact parameter b
0.090
Rp / R★
0.025163
Transit midpoint (BJD)
2,455,003.6633
Photometric dip
Transit produces a flux drop of 794 ppm lasting ≈ 1.81 h.
Extended Orbital Architecture
Planet / star radius ratio
0.025163
Semi-major axis / stellar radius
9.690
Impact parameter (b)
0.090
Transit mid-time (BJD)
2,455,003.6633
Angular separation (arcsec)
0.04360
Eq. Temperature
1,237K
(964 °C)
Insolation (S⊕)
343.60
Earth = 1.00
Earth Similarity (ESI)
0.194
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched. Close-orbiting tidally-locked around a cool host.
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-257
Spectral Class
K-type orange
Effective Temperature
5,180 K — cooler than the Sun (5,778 K)
Estimated Age
1.48 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
1.037 R☉
Stellar Mass
0.916 M☉
Metallicity [Fe/H]
0.40
Extended Stellar Properties
Surface gravity (log g)
4.360 dex
Stellar density
1.630 g/cm³
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 16 bands
Astrometric Data
Parallax
1.254 mas
Total Proper Motion
3.153 mas/yr
PM Right Ascension
3.14 mas/yr
PM Declination
0.30 mas/yr
Galactic Cartesian (pc)
x = 0.319 · y = -0.617 · z = 0.720
Equatorial (J2000)
RA 297.31600° · Dec 46.02326°
Galactic ℓ, b
79.871° · 10.012°
Ecliptic λ, β
318.712° · 64.910°
HTM-20 index
-2132779053
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HD 110067 f
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