Key parameters at a glance
- A radius of 0.88 Earth radii
- A mass of 0.62 Earth masses
- Surface gravity around 0.79 g
- An orbital period of 6.834 days
- Semi-major axis 0.0618 AU
- Equilibrium temperature 636 K (363 °C)
- Distance from Earth 578.45 light-years
- Earth Similarity Index 0.497
- Travel time at Voyager 1 speed 10,201,035 years
- Almost certainly tidally locked to its host star given the close orbit
2 siblings around Kepler-398
Kepler-398 d 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-398 b | Rocky Terrestrial | 0.93 | 0.75 | 4.081 | 755 | 2014 |
| Kepler-398 d this | Rocky Terrestrial | 0.88 | 0.62 | 6.834 | 636 | 2016 |
| Kepler-398 c | Rocky Terrestrial | 1.01 | 1.01 | 11.419 | 536 | 2014 |
Kepler-398 d Planet Profile
Physical Specs
Classification
Planet Type
Rocky Terrestrial
Discovery
Size rank in cohort
Rank by radius
#430of 570
top 75.3%
This planet
0.88R⊕
Rocky Terrestrial median
1.01R⊕
Nearest-size peers
| Metric | Earth | Kepler-398 d | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 0.88 | 11.21 |
| Mass (M⊕) | 1.00 | 0.62 | 317.83 |
| Density (g/cm³) | 5.51 | 4.96 | 1.33 |
| Surface Gravity (g) | 1.00 | 0.79 | 2.53 |
| Insolation (S⊕) | 1.00 | 40.83 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 137155210
Gaia DR2
Gaia DR2 2053457644144430848
Gaia DR3
Gaia DR3 2053457644144430848
System
Kepler-398
Percentile among Rocky Terrestrial cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 6.83 Earth days (1.9% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0618 AU.
Transit Fingerprint
Depth
0.017 %
Duration
2.154 h
Impact parameter b
0.320
Rp / R★
0.011744
Transit midpoint (BJD)
2,454,969.8635
Photometric dip
Transit produces a flux drop of 173 ppm lasting ≈ 2.15 h.
Extended Orbital Architecture
Planet / star radius ratio
0.011744
Semi-major axis / stellar radius
11.990
Impact parameter (b)
0.320
Transit mid-time (BJD)
2,454,969.8635
Angular separation (arcsec)
0.34800
Eq. Temperature
636K
(363 °C)
Insolation (S⊕)
40.83
Earth = 1.00
Earth Similarity (ESI)
0.497
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
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-398
Spectral Class
K-type orange
Effective Temperature
4,557 K — cooler than the Sun (5,778 K)
Estimated Age
2.34 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.670 R☉
Stellar Mass
0.720 M☉
Metallicity [Fe/H]
-0.06
Extended Stellar Properties
Surface gravity (log g)
4.640 dex
Stellar density
0.378 g/cm³
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 16 bands
Astrometric Data
Parallax
5.610 mas
Total Proper Motion
44.396 mas/yr
PM Right Ascension
30.66 mas/yr
PM Declination
-32.11 mas/yr
Galactic Cartesian (pc)
x = 0.279 · y = -0.709 · z = 0.647
Equatorial (J2000)
RA 291.46885° · Dec 40.34370°
Galactic ℓ, b
72.746° · 11.166°
Ecliptic λ, β
305.346° · 61.174°
HTM-20 index
1642014504
Similar Worlds
Kepler-353 b
Rocky Terrestrial · K-type orange
Radius 0.89 R⊕ · 1,254.7 ly
Kepler-1152 b
Rocky Terrestrial · K-type orange
Radius 0.87 R⊕ · 702.0 ly
Kepler-607 b
Rocky Terrestrial · K-type orange
Radius 0.87 R⊕ · 1,693.1 ly
Kepler-1907 b
Rocky Terrestrial · K-type orange
Radius 0.87 R⊕ · 952.7 ly
K2-209 b
Rocky Terrestrial · K-type orange
Radius 0.87 R⊕ · 249.5 ly
HD 21749 c
Rocky Terrestrial · K-type orange
Radius 0.89 R⊕ · 53.2 ly