Key parameters at a glance
- A radius of 13.00 Earth radii
- A mass of 1,204.26 Earth masses
- Surface gravity around 7.13 g
- An orbital period of 921.538 days
- Semi-major axis 1.7400 AU
- Distance from Earth 53.26 light-years
- Earth Similarity Index 0.413
- Travel time at Voyager 1 speed 939,217 years
1 sibling around HD 128311
HD 128311 c 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 |
|---|---|---|---|---|---|---|
| HD 128311 b | Gas Giant | 13.50 | 562.24 | 453.019 | — | 2002 |
| HD 128311 c this | Gas Giant | 13.00 | 1,204.26 | 921.538 | — | 2005 |
HD 128311 c Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#960of 1771
top 54.2%
This planet
13.00R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | HD 128311 c | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 13.00 | 11.21 |
| Mass (M⊕) | 1.00 | 1,204.26 | 317.83 |
| Density (g/cm³) | 5.51 | 3.01 | 1.33 |
| Surface Gravity (g) | 1.00 | 7.13 | 2.53 |
| Insolation (S⊕) | 1.00 | — | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 1,204.258 M⊕ | Direct mass measurement (not derived). |
| Minimum mass (M sin i) | 993.219 M⊕ | Lower bound from radial-velocity fitting. |
| Computed mass | 1,198.700 M⊕ | Model-computed mass (e.g. from mass-radius relation). |
Star Catalogue Identifiers
HD
HD 128311
HIP
HIP 71395
TIC
TIC 349606708
Gaia DR2
Gaia DR2 1176209886733406592
Gaia DR3
Gaia DR3 1176209886733406592
System
HD 128311
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts about 2.52 Earth years on a mildly elliptical path at a mean orbital distance of 1.7400 AU.
Extended Orbital Architecture
RV semi-amplitude (K)
74.799 m/s
Transit mid-time (BJD)
2,455,219.0000
Long. of periastron (ω)
15.45°
Angular separation (arcsec)
107.00000
Eq. Temperature
—
Insolation (S⊕)
—
Earth = 1.00
Earth Similarity (ESI)
0.413
0 = alien, 1 = Earth-identical
Detection Signatures
Radial velocity
Stellar wobble has been measured spectroscopically.
Astrometry
Positional wobble of the host star was measured.
Discovery Paper
Primary reference
Vogt et al. 2005Instrument
HIRES Spectrometer
Publication
2005-10
Observation locale
Ground
Discovery cohort
Planets confirmed in 2005 at W. M. Keck Observatory (12 shown).
Host System: HD 128311
Spectral Class
K-type orange
Effective Temperature
4,965 K — cooler than the Sun (5,778 K)
Estimated Age
0.96 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.760 R☉
Stellar Mass
0.828 M☉
Metallicity [Fe/H]
0.08
Extended Stellar Properties
Surface gravity (log g)
4.610 dex
Stellar density
2.609 g/cm³
Systemic radial velocity
-9.62 km/s
Rotational v·sin i
3.65 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 12 bands
Astrometric Data
Parallax
61.211 mas
Total Proper Motion
323.200 mas/yr
PM Right Ascension
204.36 mas/yr
PM Declination
-250.39 mas/yr
Galactic Cartesian (pc)
x = -0.766 · y = -0.620 · z = 0.169
Equatorial (J2000)
RA 219.00323° · Dec 9.74544°
Galactic ℓ, b
2.729° · 59.836°
Ecliptic λ, β
213.226° · 23.706°
HTM-20 index
-489393998
Observation Record
Photometric series
1
RV measurements
3
Stellar spectra
3
Archive notes
2
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