Key parameters at a glance
- A radius of 2.60 Earth radii
- A mass of 24.10 Earth masses
- Surface gravity around 3.57 g
- An orbital period of 4.137 days
- Semi-major axis 0.0480 AU
- Equilibrium temperature 863 K (590 °C)
- Distance from Earth 125.78 light-years
- Earth Similarity Index 0.296
- Travel time at Voyager 1 speed 2,218,184 years
- Almost certainly tidally locked to its host star given the close orbit
HD 18599 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1017of 1978
top 51.4%
This planet
2.60R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | HD 18599 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.60 | 11.21 |
| Mass (M⊕) | 1.00 | 24.10 | 317.83 |
| Density (g/cm³) | 5.51 | 7.50 | 1.33 |
| Surface Gravity (g) | 1.00 | 3.57 | 2.53 |
| Insolation (S⊕) | 1.00 | 145.00 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 24.100 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
HD
HD 18599
HIP
HIP 13754
TIC
TIC 207141131
Gaia DR2
Gaia DR2 4728513943538448512
Gaia DR3
Gaia DR3 4728513943538448512
System
HD 18599
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 4.14 Earth days (1.1% of a terrestrial year) on a highly eccentric trajectory at a mean orbital distance of 0.0480 AU.
Transit Fingerprint
Depth
0.113 %
Duration
2.060 h
Impact parameter b
0.500
Rp / R★
0.030900
Transit midpoint (BJD)
2,459,111.7395
Photometric dip
Transit produces a flux drop of 1,126 ppm lasting ≈ 2.06 h.
Extended Orbital Architecture
Planet / star radius ratio
0.030900
Semi-major axis / stellar radius
14.100
Impact parameter (b)
0.500
RV semi-amplitude (K)
11.300 m/s
Transit mid-time (BJD)
2,459,111.7395
Long. of periastron (ω)
-2.50°
Angular separation (arcsec)
1.24000
Eq. Temperature
863K
(590 °C)
Insolation (S⊕)
145.00
Earth = 1.00
Earth Similarity (ESI)
0.296
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
Desidera et al. 2022Instrument
TESS CCD Array
Publication
2022-10
Observation locale
Space
Discovery cohort
Planets confirmed in 2022 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).
Host System: HD 18599
Spectral Class
K-type orange
Effective Temperature
5,145 K — cooler than the Sun (5,778 K)
Estimated Age
0.40 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.767 R☉
Stellar Mass
0.863 M☉
Metallicity [Fe/H]
0.00
Extended Stellar Properties
Surface gravity (log g)
4.540 dex
Stellar density
2.241 g/cm³
Systemic radial velocity
-0.48 km/s
Rotational v·sin i
4.50 km/s
Rotation period
8.73 days
Activity index (log R'HK)
-4.350
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
25.901 mas
Total Proper Motion
62.493 mas/yr
PM Right Ascension
-36.68 mas/yr
PM Declination
50.60 mas/yr
Galactic Cartesian (pc)
x = 0.398 · y = 0.388 · z = -0.831
Equatorial (J2000)
RA 44.26201° · Dec -56.19187°
Galactic ℓ, b
273.928° · -53.278°
Ecliptic λ, β
3.698° · -66.465°
HTM-20 index
962272501
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