Key parameters at a glance
- A radius of 4.43 Earth radii
- A mass of 44.00 Earth masses
- Surface gravity around 2.24 g
- An orbital period of 2.849 days
- Semi-major axis 0.0349 AU
- Equilibrium temperature 900 K (627 °C)
- Distance from Earth 520.29 light-years
- Earth Similarity Index 0.250
- Travel time at Voyager 1 speed 9,175,324 years
- Almost certainly tidally locked to its host star given the close orbit
K2-55 b Planet Profile
Physical Specs
Classification
Planet Type
Neptune-like
Discovery
Size rank in cohort
Rank by radius
#468of 574
top 81.4%
This planet
4.43R⊕
Neptune-like median
6.39R⊕
Nearest-size peers
| Metric | Earth | K2-55 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 4.43 | 11.21 |
| Mass (M⊕) | 1.00 | 44.00 | 317.83 |
| Density (g/cm³) | 5.51 | 2.80 | 1.33 |
| Surface Gravity (g) | 1.00 | 2.24 | 2.53 |
| Insolation (S⊕) | 1.00 | 141.30 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 44.000 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 437704321
Gaia DR2
Gaia DR2 6825931948041984256
Gaia DR3
Gaia DR3 6825931948041984256
System
K2-55
Percentile among Neptune-like cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 2.85 Earth days (0.8% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0349 AU.
Transit Fingerprint
Depth
0.395 %
Duration
2.006 h
Impact parameter b
0.140
Rp / R★
0.056128
Transit midpoint (BJD)
2,456,983.4229
Photometric dip
Transit produces a flux drop of 3,954 ppm lasting ≈ 2.01 h.
Extended Orbital Architecture
Planet / star radius ratio
0.056128
Semi-major axis / stellar radius
10.500
Impact parameter (b)
0.140
Transit mid-time (BJD)
2,456,983.4229
Long. of periastron (ω)
23.90°
Angular separation (arcsec)
0.21900
Eq. Temperature
900K
(627 °C)
Insolation (S⊕)
141.30
Earth = 1.00
Earth Similarity (ESI)
0.250
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
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: K2-55
Spectral Class
K-type orange
Effective Temperature
4,300 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.715 R☉
Stellar Mass
0.688 M☉
Metallicity [Fe/H]
0.38
Extended Stellar Properties
Surface gravity (log g)
4.566 dex
Stellar density
2.351 g/cm³
Systemic radial velocity
3.95 km/s
Rotational v·sin i
2.20 km/s
Activity index (log R'HK)
-4.734
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 12 bands
Astrometric Data
Parallax
6.240 mas
Total Proper Motion
25.431 mas/yr
PM Right Ascension
-12.59 mas/yr
PM Declination
-22.10 mas/yr
Galactic Cartesian (pc)
x = 0.857 · y = -0.422 · z = -0.297
Equatorial (J2000)
RA 333.75188° · Dec -17.25080°
Galactic ℓ, b
39.933° · -52.632°
Ecliptic λ, β
329.450° · -5.974°
HTM-20 index
-2045457626
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