Key parameters at a glance
- A radius of 2.00 Earth radii
- A mass of 4.66 Earth masses
- Surface gravity around 1.17 g
- An orbital period of 6.034 days
- Semi-major axis 0.0513 AU
- Equilibrium temperature 586 K (313 °C)
- Distance from Earth 237.80 light-years
- Earth Similarity Index 0.466
- Travel time at Voyager 1 speed 4,193,638 years
- Almost certainly tidally locked to its host star given the close orbit
1 sibling around K2-240
K2-240 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 |
|---|---|---|---|---|---|---|
| K2-240 b this | Sub-Neptune | 2.00 | 4.66 | 6.034 | 586 | 2018 |
| K2-240 c | Super-Earth | 1.80 | 3.89 | 20.523 | 389 | 2018 |
K2-240 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1955of 1978
top 98.8%
This planet
2.00R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | K2-240 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.00 | 11.21 |
| Mass (M⊕) | 1.00 | 4.66 | 317.83 |
| Density (g/cm³) | 5.51 | 3.20 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.17 | 2.53 |
| Insolation (S⊕) | 1.00 | — | 0.037 |
Star Catalogue Identifiers
TIC
TIC 432247315
Gaia DR2
Gaia DR2 6257625719430982016
Gaia DR3
Gaia DR3 6257625719430982016
System
K2-240
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 6.03 Earth days (1.7% of a terrestrial year) at a mean orbital distance of 0.0513 AU.
Transit Fingerprint
Depth
0.131 %
Duration
2.153 h
Impact parameter b
0.280
Rp / R★
0.036200
Transit midpoint (BJD)
2,457,996.8250
Photometric dip
Transit produces a flux drop of 1,310 ppm lasting ≈ 2.15 h.
Extended Orbital Architecture
Planet / star radius ratio
0.036200
Semi-major axis / stellar radius
21.100
Impact parameter (b)
0.280
Transit mid-time (BJD)
2,457,996.8250
Angular separation (arcsec)
0.70400
Eq. Temperature
586K
(313 °C)
Insolation (S⊕)
—
Earth = 1.00
Earth Similarity (ESI)
0.466
0 = alien, 1 = Earth-identical
Insufficient insolation data — the surface is too hot to retain surface water. Close-orbiting tidally-locked around a cool host.
Discovery Paper
Primary reference
D Iacute Ez Alonso et al. 2018Instrument
Kepler CCD Array
Publication
2018-10
Observation locale
Space
Discovery cohort
Planets confirmed in 2018 at K2 (12 shown).
Host System: K2-240
Spectral Class
M-type red dwarf
Effective Temperature
3,810 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.540 R☉
Stellar Mass
0.580 M☉
Metallicity [Fe/H]
-0.10
Extended Stellar Properties
Surface gravity (log g)
4.700 dex
Stellar density
4.329 g/cm³
Systemic radial velocity
0.61 km/s
Rotation period
10.80 days
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 13 bands
Astrometric Data
Parallax
13.688 mas
Total Proper Motion
75.010 mas/yr
PM Right Ascension
-53.75 mas/yr
PM Declination
-52.32 mas/yr
Galactic Cartesian (pc)
x = -0.639 · y = -0.706 · z = -0.307
Equatorial (J2000)
RA 227.84937° · Dec -17.87545°
Galactic ℓ, b
343.891° · 33.639°
Ecliptic λ, β
230.302° · -0.054°
HTM-20 index
-1170444833
Similar Worlds
L 363-38 b
Sub-Neptune · M-type red dwarf
Radius 2.00 R⊕ · 33.4 ly
Kepler-236 c
Sub-Neptune · M-type red dwarf
Radius 2.00 R⊕ · 941.8 ly
K2-153 b
Sub-Neptune · M-type red dwarf
Radius 2.00 R⊕ · 466.8 ly
Kepler-296 c
Sub-Neptune · M-type red dwarf
Radius 2.00 R⊕ · 544.7 ly
Kepler-32 c
Sub-Neptune · M-type red dwarf
Radius 2.00 R⊕ · 1,056.2 ly
K2-150 b
Sub-Neptune · M-type red dwarf
Radius 2.00 R⊕ · 334.3 ly