Key parameters at a glance
- A radius of 2.22 Earth radii
- A mass of 12.90 Earth masses
- Surface gravity around 2.63 g
- An orbital period of 81.738 days
- Semi-major axis 0.3554 AU
- Equilibrium temperature 417 K (144 °C)
- Distance from Earth 508.66 light-years
- Earth Similarity Index 0.627
- Travel time at Voyager 1 speed 8,970,216 years
Kepler-538 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1654of 1978
top 83.6%
This planet
2.22R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | Kepler-538 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.22 | 11.21 |
| Mass (M⊕) | 1.00 | 12.90 | 317.83 |
| Density (g/cm³) | 5.51 | 6.50 | 1.33 |
| Surface Gravity (g) | 1.00 | 2.63 | 2.53 |
| Insolation (S⊕) | 1.00 | 5.07 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 12.900 M⊕ | Direct mass measurement (not derived). |
| Minimum mass (M sin i) | 10.460 M⊕ | Lower bound from radial-velocity fitting. |
Star Catalogue Identifiers
TIC
TIC 28227113
Gaia DR2
Gaia DR2 2087171453788422528
Gaia DR3
Gaia DR3 2087171453788422528
System
Kepler-538
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 81.74 Earth days (22.4% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.3554 AU.
Transit Fingerprint
Depth
0.064 %
Duration
6.701 h
Impact parameter b
0.037
Rp / R★
0.022911
Transit midpoint (BJD)
2,455,044.6789
Photometric dip
Transit produces a flux drop of 642 ppm lasting ≈ 6.70 h.
Extended Orbital Architecture
Planet / star radius ratio
0.022911
Semi-major axis / stellar radius
95.265
Impact parameter (b)
0.037
RV semi-amplitude (K)
2.090 m/s
Transit mid-time (BJD)
2,455,044.6789
Long. of periastron (ω)
140.00°
Angular separation (arcsec)
2.28000
Eq. Temperature
417K
(144 °C)
Insolation (S⊕)
5.07
Earth = 1.00
Earth Similarity (ESI)
0.627
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.
Detection Signatures
Transit photometry
A transit dip has been observed from at least one telescope.
Radial velocity
Stellar wobble has been measured spectroscopically.
Discovery Paper
Primary reference
Morton et al. 2016Instrument
Kepler CCD Array
Publication
2016-05
Observation locale
Space
Discovery cohort
Planets confirmed in 2016 at Kepler (12 shown).
Host System: Kepler-538
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
5,534 K — cooler than the Sun (5,778 K)
Estimated Age
5.30 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.872 R☉
Stellar Mass
0.892 M☉
Metallicity [Fe/H]
-0.09
Extended Stellar Properties
Surface gravity (log g)
4.510 dex
Stellar density
1.390 g/cm³
Systemic radial velocity
-37.32 km/s
Rotational v·sin i
1.10 km/s
Rotation period
25.20 days
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 16 bands
Astrometric Data
Parallax
6.383 mas
Total Proper Motion
49.967 mas/yr
PM Right Ascension
-49.31 mas/yr
PM Declination
-8.05 mas/yr
Galactic Cartesian (pc)
x = 0.299 · y = -0.575 · z = 0.762
Equatorial (J2000)
RA 297.48655° · Dec 49.62340°
Galactic ℓ, b
83.142° · 11.641°
Ecliptic λ, β
323.127° · 68.054°
HTM-20 index
1420293777
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