Key parameters at a glance
- A radius of 1.42 Earth radii
- A mass of 2.60 Earth masses
- Surface gravity around 1.29 g
- An orbital period of 5.676 days
- Semi-major axis 0.0560 AU
- Distance from Earth 373.90 light-years
- Earth Similarity Index 0.912
- Travel time at Voyager 1 speed 6,593,646 years
- Almost certainly tidally locked to its host star given the close orbit
K2-128 b Planet Profile
Physical Specs
Classification
Planet Type
Super-Earth
Discovery
Size rank in cohort
Rank by radius
#884of 1176
top 75.1%
This planet
1.42R⊕
Super-Earth median
1.60R⊕
Nearest-size peers
| Metric | Earth | K2-128 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 1.42 | 11.21 |
| Mass (M⊕) | 1.00 | 2.60 | 317.83 |
| Density (g/cm³) | 5.51 | 4.99 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.29 | 2.53 |
| Insolation (S⊕) | 1.00 | 68.80 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 677945
Gaia DR2
Gaia DR2 3618386664139093504
Gaia DR3
Gaia DR3 3618386664139093504
System
K2-128
Percentile among Super-Earth cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 5.68 Earth days (1.6% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0560 AU.
Transit Fingerprint
Depth
0.033 %
Duration
1.805 h
Rp / R★
0.016752
Transit midpoint (BJD)
2,457,255.5030
Photometric dip
Transit produces a flux drop of 332 ppm lasting ≈ 1.80 h.
Extended Orbital Architecture
Planet / star radius ratio
0.016752
Semi-major axis / stellar radius
15.460
Transit mid-time (BJD)
2,457,255.5030
Long. of periastron (ω)
62.55°
Angular separation (arcsec)
0.48800
Eq. Temperature
—
Insolation (S⊕)
68.80
Earth = 1.00
Earth Similarity (ESI)
0.912
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water). Close-orbiting tidally-locked around a cool host.
Discovery Paper
Primary reference
Dressing et al. 2017Instrument
Kepler CCD Array
Publication
2017-11
Observation locale
Space
Discovery cohort
Planets confirmed in 2017 at K2 (12 shown).
Host System: K2-128
Spectral Class
K-type orange
Effective Temperature
4,470 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.778 R☉
Stellar Mass
0.711 M☉
Metallicity [Fe/H]
-0.26
Extended Stellar Properties
Surface gravity (log g)
4.700 dex
Stellar density
3.005 g/cm³
Systemic radial velocity
-13.21 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 12 bands
Astrometric Data
Parallax
8.695 mas
Total Proper Motion
4.590 mas/yr
PM Right Ascension
1.41 mas/yr
PM Declination
-4.37 mas/yr
Galactic Cartesian (pc)
x = -0.900 · y = -0.409 · z = -0.149
Equatorial (J2000)
RA 204.43767° · Dec -8.59709°
Galactic ℓ, b
321.981° · 52.553°
Ecliptic λ, β
205.775° · 1.465°
HTM-20 index
-758350993
Similar Worlds
Kepler-763 c
Super-Earth · K-type orange
Radius 1.42 R⊕ · 3,139.1 ly
Kepler-1075 b
Super-Earth · K-type orange
Radius 1.42 R⊕ · 950.0 ly
TOI-286 b
Super-Earth · K-type orange
Radius 1.42 R⊕ · 193.2 ly
Kepler-1825 b
Super-Earth · K-type orange
Radius 1.42 R⊕ · 1,403.3 ly
Kepler-1038 c
Super-Earth · K-type orange
Radius 1.42 R⊕ · 1,905.2 ly
Kepler-1813 b
Super-Earth · K-type orange
Radius 1.41 R⊕ · —