Key parameters at a glance
- A radius of 4.90 Earth radii
- A mass of 17.60 Earth masses
- Surface gravity around 0.73 g
- An orbital period of 6.034 days
- Semi-major axis 0.0636 AU
- Equilibrium temperature 1,076 K (803 °C)
- Distance from Earth 307.15 light-years
- Earth Similarity Index 0.171
- Travel time at Voyager 1 speed 5,416,542 years
HD 219666 b Planet Profile
Physical Specs
Classification
Planet Type
Neptune-like
Discovery
Size rank in cohort
Rank by radius
#400of 574
top 69.5%
This planet
4.90R⊕
Neptune-like median
6.39R⊕
Nearest-size peers
| Metric | Earth | HD 219666 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 4.90 | 11.21 |
| Mass (M⊕) | 1.00 | 17.60 | 317.83 |
| Density (g/cm³) | 5.51 | 0.87 | 1.33 |
| Surface Gravity (g) | 1.00 | 0.73 | 2.53 |
| Insolation (S⊕) | 1.00 | 598.44 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 17.600 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
HD
HD 219666
TIC
TIC 266980320
Gaia DR2
Gaia DR2 6492940453524576128
Gaia DR3
Gaia DR3 6492940453524576128
System
HD 219666
Percentile among Neptune-like cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 6.03 Earth days (1.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0636 AU.
Transit Fingerprint
Depth
0.175 %
Duration
2.158 h
Impact parameter b
0.838
Rp / R★
0.042100
Transit midpoint (BJD)
2,459,083.5107
Photometric dip
Transit produces a flux drop of 1,751 ppm lasting ≈ 2.16 h.
Extended Orbital Architecture
Planet / star radius ratio
0.042100
Semi-major axis / stellar radius
13.250
Impact parameter (b)
0.838
RV semi-amplitude (K)
6.070 m/s
Transit mid-time (BJD)
2,459,083.5107
Long. of periastron (ω)
0.00°
Angular separation (arcsec)
0.67500
Eq. Temperature
1,076K
(803 °C)
Insolation (S⊕)
598.44
Earth = 1.00
Earth Similarity (ESI)
0.171
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.
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
Esposito et al. 2019Instrument
TESS CCD Array
Publication
2019-03
Observation locale
Space
Discovery cohort
Planets confirmed in 2018 at Transiting Exoplanet Survey Satellite (TESS) (2 shown).
Host System: HD 219666
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
5,540 K — cooler than the Sun (5,778 K)
Estimated Age
10.00 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
1.059 R☉
Stellar Mass
1.020 M☉
Metallicity [Fe/H]
0.04
Extended Stellar Properties
Surface gravity (log g)
4.400 dex
Stellar density
1.176 g/cm³
Systemic radial velocity
-20.10 km/s
Rotational v·sin i
2.20 km/s
Activity index (log R'HK)
-5.070
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
10.590 mas
Total Proper Motion
314.566 mas/yr
PM Right Ascension
313.92 mas/yr
PM Declination
-20.18 mas/yr
Galactic Cartesian (pc)
x = 0.537 · y = -0.099 · z = -0.838
Equatorial (J2000)
RA 349.55927° · Dec -56.90399°
Galactic ℓ, b
325.609° · -55.929°
Ecliptic λ, β
321.701° · -46.825°
HTM-20 index
1364149778
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