Key parameters at a glance
- A radius of 2.34 Earth radii
- A mass of 6.08 Earth masses
- Surface gravity around 1.11 g
- An orbital period of 3.177 days
- Semi-major axis 0.0390 AU
- Equilibrium temperature 997 K (724 °C)
- Distance from Earth 1,665.10 light-years
- Earth Similarity Index 0.257
- Travel time at Voyager 1 speed 29,364,061 years
1 sibling around Kepler-121
Kepler-121 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-121 b this | Sub-Neptune | 2.34 | 6.08 | 3.177 | 997 | 2014 |
| Kepler-121 c | Sub-Neptune | 2.27 | 5.77 | 41.008 | 425 | 2014 |
Kepler-121 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1429of 1978
top 72.2%
This planet
2.34R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | Kepler-121 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.34 | 11.21 |
| Mass (M⊕) | 1.00 | 6.08 | 317.83 |
| Density (g/cm³) | 5.51 | 2.61 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.11 | 2.53 |
| Insolation (S⊕) | 1.00 | 220.49 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 120765800
Gaia DR2
Gaia DR2 2100654421280638976
Gaia DR3
Gaia DR3 2100654421280638976
System
Kepler-121
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 3.18 Earth days (0.9% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0390 AU.
Transit Fingerprint
Depth
0.113 %
Duration
1.475 h
Impact parameter b
0.110
Rp / R★
0.031455
Transit midpoint (BJD)
2,454,967.4779
Photometric dip
Transit produces a flux drop of 1,134 ppm lasting ≈ 1.48 h.
Extended Orbital Architecture
Planet / star radius ratio
0.031455
Semi-major axis / stellar radius
17.098
Impact parameter (b)
0.110
Transit mid-time (BJD)
2,454,967.4779
Angular separation (arcsec)
0.07640
Eq. Temperature
997K
(724 °C)
Insolation (S⊕)
220.49
Earth = 1.00
Earth Similarity (ESI)
0.257
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.
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-121
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
5,311 K — cooler than the Sun (5,778 K)
Estimated Age
0.50 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.701 R☉
Stellar Mass
0.859 M☉
Metallicity [Fe/H]
-0.08
Extended Stellar Properties
Surface gravity (log g)
4.646 dex
Stellar density
9.365 g/cm³
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 17 bands
Astrometric Data
Parallax
1.930 mas
Total Proper Motion
11.050 mas/yr
PM Right Ascension
11.00 mas/yr
PM Declination
1.07 mas/yr
Galactic Cartesian (pc)
x = 0.214 · y = -0.739 · z = 0.638
Equatorial (J2000)
RA 286.16213° · Dec 39.67802°
Galactic ℓ, b
70.379° · 14.576°
Ecliptic λ, β
296.788° · 61.622°
HTM-20 index
-1876311070
Similar Worlds
Kepler-171 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.34 R⊕ · 2,817.5 ly
Kepler-29 c
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.34 R⊕ · 2,715.4 ly
HD 158259 e
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.34 R⊕ · 88.2 ly
Kepler-338 c
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.34 R⊕ · 1,803.0 ly
Kepler-213 c
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.34 R⊕ · 2,070.9 ly
Kepler-246 b
Sub-Neptune · G-type yellow (Sun-like)
Radius 2.34 R⊕ · 2,042.0 ly