Key parameters at a glance
- A radius of 2.50 Earth radii
- A mass of 603.88 Earth masses
- Surface gravity around 96.65 g
- An orbital period of 8.200 days
- Semi-major axis 0.0753 AU
- Equilibrium temperature 806 K (533 °C)
- Distance from Earth 462.26 light-years
- Earth Similarity Index 0.167
- Travel time at Voyager 1 speed 8,152,028 years
- Almost certainly tidally locked to its host star given the close orbit
K2-77 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1189of 1978
top 60.1%
This planet
2.50R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-77 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.50 | 11.21 |
| Mass (M⊕) | 1.00 | 603.88 | 317.83 |
| Density (g/cm³) | 5.51 | — | 1.33 |
| Surface Gravity (g) | 1.00 | 96.65 | 2.53 |
| Insolation (S⊕) | 1.00 | 58.00 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 603.877 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 435339847
Gaia DR2
Gaia DR2 37619725922094336
Gaia DR3
Gaia DR3 37619725922094336
System
K2-77
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 8.20 Earth days (2.2% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0753 AU.
Transit Fingerprint
Depth
0.083 %
Duration
2.544 h
Impact parameter b
0.550
Rp / R★
0.028800
Transit midpoint (BJD)
2,457,316.8077
Photometric dip
Transit produces a flux drop of 831 ppm lasting ≈ 2.54 h.
Extended Orbital Architecture
Planet / star radius ratio
0.028800
Semi-major axis / stellar radius
20.460
Impact parameter (b)
0.550
Transit mid-time (BJD)
2,457,316.8077
Long. of periastron (ω)
-40.00°
Angular separation (arcsec)
0.53100
Eq. Temperature
806K
(533 °C)
Insolation (S⊕)
58.00
Earth = 1.00
Earth Similarity (ESI)
0.167
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
Crossfield et al. 2016Instrument
Kepler CCD Array
Publication
2016-09
Observation locale
Space
Discovery cohort
Planets confirmed in 2016 at K2 (12 shown).
Host System: K2-77
Spectral Class
K-type orange
Effective Temperature
5,160 K — cooler than the Sun (5,778 K)
Estimated Age
4.70 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.792 R☉
Stellar Mass
0.847 M☉
Metallicity [Fe/H]
0.13
Extended Stellar Properties
Surface gravity (log g)
4.569 dex
Stellar density
2.410 g/cm³
Systemic radial velocity
7.35 km/s
Rotational v·sin i
4.00 km/s
Rotation period
19.80 days
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 15 bands
Astrometric Data
Parallax
7.027 mas
Total Proper Motion
44.110 mas/yr
PM Right Ascension
22.56 mas/yr
PM Declination
-37.91 mas/yr
Galactic Cartesian (pc)
x = 0.557 · y = 0.802 · z = 0.218
Equatorial (J2000)
RA 55.22852° · Dec 12.57245°
Galactic ℓ, b
174.467° · -32.855°
Ecliptic λ, β
55.897° · -6.846°
HTM-20 index
948821543
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