Space Codex / Exoplanet reference
Published exoplanet measurements
HD 128311 b
HD 128311 b orbits HD 128311 once every 453.019 days. The system is about 53.2587 light-years from Earth.
Archive retrieved November 1, 2026 (America/New_York). The selected paper and archive update dates appear below.
The recorded orbit
The selected archive solution gives an orbital period of 453.019 days, or 1.2403 Earth years. Its reported semimajor axis is 1.084 AU. That orbital scale is 2.80032 times Mercury's semimajor axis. The listed eccentricity is 0.303. Using those central values, the model's nearest and farthest star–planet distances are about 0.755548 and 1.41245 AU. These are derived comparisons, without propagated errors. The period measures a year on this planet. It does not establish the length of its rotation or the duration of daylight.
Read how orbital period, size, and eccentricity fit together.
Size and mass
No planetary radius is supplied in this selected solution. The profile leaves that gap visible rather than estimating a size from the mass. The mass parameter is 562.241 (+7.31009 / −7.31009) Earth masses. Its archive provenance is Msini. Read this provenance before comparing it with a true mass: an inclination-dependent minimum or another mass definition must keep its qualification.
The host star and received light
The host is cataloged as HD 128311. Its reported radius is 0.76 solar radii. Its reported mass is 0.828 solar masses. The available stellar and orbital entries do not establish a breathable atmosphere, surface water, or life.
What a habitable-zone claim does and does not mean · How a star changes over time.
Other planets around HD 128311
The fetched archive contains 2 selected default planet records for this host. This is the retrieved record set, and additional or revised discoveries may appear in later research.
| Planet | Period (days) | Radius (Earth) | Mass parameter (Earth) | Mass definition |
|---|---|---|---|---|
| HD 128311 b | 453.019 (+0.404 / −0.404) | Not reported in this solution | 562.241 (+7.31009 / −7.31009) | Msini |
| HD 128311 c | 921.538 (+1.15 / −1.15) | Not reported in this solution | 1204.26 (+293.675 / −137.303) | Mass |
Earth comparison
| Quantity | Reported value or conversion | Comparison |
|---|---|---|
| Orbital period | 453.019 days | 1.2403 Earth years |
| System distance | 16.3292 parsecs | 53.2587 light-years |
| Orbital scale | 1.084 (+0.006 / −0.006) | AU; Earth = 1 |
| Mass parameter | 562.241 (+7.31009 / −7.31009) | Earth masses; check mass definition |
Conversions use rounded central values. They are navigation aids for the data, not additional observations. Uncertainties for the original parameters remain in the next table.
Measurement table
| Parameter | Value and reported uncertainty | Unit or definition |
|---|---|---|
| Orbital period | 453.019 (+0.404 / −0.404) | days |
| Semimajor axis | 1.084 (+0.006 / −0.006) | AU |
| Radius | Not reported in this solution | Earth radii |
| Mass parameter | 562.241 (+7.31009 / −7.31009) | Earth masses |
| Orbital eccentricity | 0.303 (+0.011 / −0.011) | dimensionless |
| Orbital inclination | Lower limit: 30 | degrees |
| Equilibrium temperature | Not reported in this solution | K; model estimate |
| Incident flux | Not reported in this solution | Earth flux |
| Bulk density | Not reported in this solution | g/cm³ |
| Host effective temperature | Not reported in this solution | K |
| Host radius | 0.76 (+0.02 / −0.02) | solar radii |
| Host mass | 0.828 (+0.008 / −0.012) | solar masses |
| Host metallicity | Not reported in this solution | dex; archive abundance definition |
| Host age | Upper limit: 0.96 | billion years |
| Host luminosity | Not reported in this solution | log10 solar luminosity |
| Host surface gravity | 4.61 (+0.01 / −0.02) | log10 cm/s² |
| Host rotation period | Not reported in this solution | days |
| System distance | 16.3292 (+0.0199 / −0.0198) | parsecs |
Parentheses show the reported upper and lower uncertainties when both are supplied. Bounds are explicitly labeled. A missing entry means unavailable in this solution, not zero. The confidence convention belongs to the source paper.
Research record and limitations
| Record | Value |
|---|---|
| Planetary reference | McArthur et al. 2014 |
| Discovery method | Radial Velocity |
| Discovery year | 2002 |
| Discovery facility | W. M. Keck Observatory |
| Mass provenance | Msini |
| Host stars in system | 1 |
| Archive system planet count | 2 |
| Planetary solution publication date | 2014-11 |
| Row update date | 2015-06-24 |
| Archive release date | 2015-06-25 |
Source: NASA Exoplanet Archive overview for HD 128311 b, Planetary Systems table, default solution. The collection excludes entries flagged controversial at retrieval. A selected default is a published reference choice, not a claim that every parameter is the latest estimate in all literature.
This profile documents measurements and their scope. It is separate from the 3D planet catalog and does not create a sponsorship placement or a new explorer destination.