Key parameters at a glance
- A radius of 2.85 Earth radii
- A mass of 12.40 Earth masses
- Surface gravity around 1.53 g
- An orbital period of 7.374 days
- Semi-major axis 0.0662 AU
- Equilibrium temperature 694 K (421 °C)
- Distance from Earth 350.68 light-years
- Earth Similarity Index 0.363
- Travel time at Voyager 1 speed 6,184,178 years
- Almost certainly tidally locked to its host star given the close orbit
1 sibling around K2-199
K2-199 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 |
|---|---|---|---|---|---|---|
| K2-199 b | Super-Earth | 1.73 | 6.90 | 3.225 | 913 | 2018 |
| K2-199 c this | Sub-Neptune | 2.85 | 12.40 | 7.374 | 694 | 2018 |
K2-199 c Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#685of 1978
top 34.6%
This planet
2.85R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-199 c | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.85 | 11.21 |
| Mass (M⊕) | 1.00 | 12.40 | 317.83 |
| Density (g/cm³) | 5.51 | 2.90 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.53 | 2.53 |
| Insolation (S⊕) | 1.00 | 38.60 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 12.400 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 2621212
Gaia DR2
Gaia DR2 3620501712193719296
Gaia DR3
Gaia DR3 3620501712193719296
System
K2-199
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 7.37 Earth days (2.0% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0662 AU.
Transit Fingerprint
Depth
0.174 %
Duration
2.452 h
Impact parameter b
0.490
Rp / R★
0.038460
Transit midpoint (BJD)
2,457,222.9303
Photometric dip
Transit produces a flux drop of 1,739 ppm lasting ≈ 2.45 h.
Extended Orbital Architecture
Planet / star radius ratio
0.038460
Semi-major axis / stellar radius
20.960
Impact parameter (b)
0.490
RV semi-amplitude (K)
5.100 m/s
Transit mid-time (BJD)
2,457,222.9303
Long. of periastron (ω)
170.00°
Angular separation (arcsec)
0.61600
Eq. Temperature
694K
(421 °C)
Insolation (S⊕)
38.60
Earth = 1.00
Earth Similarity (ESI)
0.363
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.
Radial velocity
Stellar wobble has been measured spectroscopically.
Discovery Paper
Primary reference
Mayo et al. 2018Instrument
Kepler CCD Array
Publication
2018-03
Observation locale
Space
Discovery cohort
Planets confirmed in 2018 at K2 (12 shown).
Host System: K2-199
Spectral Class
K-type orange
Effective Temperature
4,491 K — cooler than the Sun (5,778 K)
Estimated Age
5.04 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.682 R☉
Stellar Mass
0.711 M☉
Metallicity [Fe/H]
-0.01
Extended Stellar Properties
Surface gravity (log g)
4.640 dex
Stellar density
2.928 g/cm³
Systemic radial velocity
1.07 km/s
Activity index (log R'HK)
-4.735
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 17 bands
Astrometric Data
Parallax
9.272 mas
Total Proper Motion
61.174 mas/yr
PM Right Ascension
-59.26 mas/yr
PM Declination
15.20 mas/yr
Galactic Cartesian (pc)
x = -0.870 · y = -0.481 · z = -0.107
Equatorial (J2000)
RA 208.90145° · Dec -6.13608°
Galactic ℓ, b
330.297° · 53.292°
Ecliptic λ, β
209.042° · 5.341°
HTM-20 index
1088697402
Similar Worlds
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Kepler-599 b
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Kepler-1388 d
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Kepler-304 b
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TOI-5789 c
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Kepler-1665 b
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Radius 2.84 R⊕ · 1,094.3 ly