Key parameters at a glance
- A radius of 8.29 Earth radii
- A mass of 120.78 Earth masses
- Surface gravity around 1.76 g
- An orbital period of 2.876 days
- Semi-major axis 0.0436 AU
- Equilibrium temperature 1,626 K (1353 °C)
- Distance from Earth 247.44 light-years
- Earth Similarity Index 0.088
- Travel time at Voyager 1 speed 4,363,533 years
HD 149026 b Planet Profile
Physical Specs
Classification
Planet Type
Neptune-like
Discovery
Size rank in cohort
Rank by radius
#136of 574
top 23.5%
This planet
8.29R⊕
Neptune-like median
6.39R⊕
Nearest-size peers
| Metric | Earth | HD 149026 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 8.29 | 11.21 |
| Mass (M⊕) | 1.00 | 120.78 | 317.83 |
| Density (g/cm³) | 5.51 | 0.75 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.76 | 2.53 |
| Insolation (S⊕) | 1.00 | 1,095.91 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 120.775 M⊕ | Direct mass measurement (not derived). |
| Minimum mass (M sin i) | 114.410 M⊕ | Lower bound from radial-velocity fitting. |
| Computed mass | 114.800 M⊕ | Model-computed mass (e.g. from mass-radius relation). |
Star Catalogue Identifiers
HD
HD 149026
HIP
HIP 80838
TIC
TIC 255930614
Gaia DR2
Gaia DR2 1331356474971716992
Gaia DR3
Gaia DR3 1331356474971716992
System
HD 149026
Percentile among Neptune-like cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 2.88 Earth days (0.8% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0436 AU.
Transit Fingerprint
Depth
0.290 %
Duration
3.140 h
Impact parameter b
0.571
Rp / R★
0.054160
Transit midpoint (BJD)
2,457,217.6414
Photometric dip
Transit produces a flux drop of 2,900 ppm lasting ≈ 3.14 h.
Extended Orbital Architecture
Planet / star radius ratio
0.054160
Semi-major axis / stellar radius
6.800
Impact parameter (b)
0.571
RV semi-amplitude (K)
43.300 m/s
Transit mid-time (BJD)
2,457,217.6414
Long. of periastron (ω)
109.00°
Sky-projected obliquity (λ)
12.00°
Angular separation (arcsec)
0.57500
Eq. Temperature
1,626K
(1353 °C)
Insolation (S⊕)
1,095.91
Earth = 1.00
Earth Similarity (ESI)
0.088
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.
Orbital-brightness modulation
Host star brightness varies with the planet's orbit.
Discovery Paper
Primary reference
Sato et al. 2005Instrument
HDS Spectrograph
Publication
2005-11
Observation locale
Ground
Host System: HD 149026
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
6,179 K — hotter than the Sun (5,778 K)
Estimated Age
2.60 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
1.410 R☉
Stellar Mass
1.420 M☉
Metallicity [Fe/H]
0.32
Extended Stellar Properties
Surface gravity (log g)
4.370 dex
Stellar density
0.720 g/cm³
Systemic radial velocity
-17.84 km/s
Rotational v·sin i
6.00 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
13.153 mas
Total Proper Motion
93.975 mas/yr
PM Right Ascension
-77.90 mas/yr
PM Declination
52.56 mas/yr
Galactic Cartesian (pc)
x = -0.299 · y = -0.725 · z = 0.620
Equatorial (J2000)
RA 247.62298° · Dec 38.34753°
Galactic ℓ, b
61.297° · 43.284°
Ecliptic λ, β
234.496° · 59.060°
HTM-20 index
-1930620041
Observation Record
Photometric series
14
RV measurements
3
Stellar spectra
4
Emission spectra
9
Archive notes
1
Similar Worlds
Kepler-9 b
Neptune-like · G-type yellow (Sun-like)
Radius 8.29 R⊕ · 2,049.1 ly
Kepler-855 b
Neptune-like · G-type yellow (Sun-like)
Radius 8.35 R⊕ · 4,913.8 ly
Kepler-539 b
Neptune-like · G-type yellow (Sun-like)
Radius 8.37 R⊕ · 1,002.3 ly
Kepler-108 c
Neptune-like · G-type yellow (Sun-like)
Radius 8.18 R⊕ · 1,104.8 ly
HD 13724 c
Neptune-like · G-type yellow (Sun-like)
Radius 8.18 R⊕ · 141.8 ly
Kepler-720 b
Neptune-like · G-type yellow (Sun-like)
Radius 8.41 R⊕ · 3,474.8 ly