Gas giant · HD 128717

HD 128717 b

ExoplanetsDiscovered 2025

Scientific overview

HD 128717 b is a gas giant orbiting HD 128717, completing an orbit every 3420 days, about 240 light-years from Earth. It was discovered in 2025 using the astrometry.

Host star

HD 128717

Temperature

6,210 K

Mass

1.212 M☉

Discovery and detection

Detection method

Astrometry

Discovery year

2025

Discovered at

Gaia

Knowledge connections

OrbitsHD 128717
Discovered by methodAstrometry
Discovered by missionGaia
Catalogued inNASA Exoplanet Archive

Quick facts

Class: Gas giant
Host star: HD 128717
Discovery method: Astrometry
Discovery year: 2025
Orbital period: 3420 d
Semi-major axis: 4.85 AU
Eccentricity: 0.85
Radius: 12.1 R⊕
Mass: 6293 M⊕
Density: 19.58 g/cm³ · derived
Equilibrium temp.: 152 K
Insolation: 0.09 S⊕
Distance: 240 ly

Density is derived from the archive mass and radius via ρ = M / (4⁄3·π·r³); all other values are catalogued measurements.

Derived values

Computed from source-backed inputs via standard formulae — not observations. Every input and constant is traced below.

Bulk density19.58 g/cm³derived
Formula & inputs
Formula: ρ = M / (4⁄3·π·r³) (v1.0.0, impl v1.0.0)
Inputs:
- massEarth = 6293 M⊕ · NASA
- radiusEarth = 12.1 R⊕ · NASA
Assumptions: M⊕ = 5.972e+24 kg, R⊕ = 6371000 m (IAU 2015 B3 nominal); Assumes a uniform sphere.
Limitations: Withheld above 30 g/cm³ (inconsistent mass/radius inputs).; Archive mass/radius carry no propagated uncertainty here.
Uncertainty: not propagated (inputs carry no catalogued uncertainty)
Computed as of 2026-06-29.

Quality & authority

Partial

Unreviewed

Description: Complete
Source coverage: Partial
Relationship coverage: Complete
Review coverage: None
Citation coverage: None
Image coverage: Not applicable

Data from the NASA Exoplanet Archive. See source quality.