Key parameters at a glance

A radius of 12.10 Earth radii
A mass of 6,293.00 Earth masses
Surface gravity around 42.98 g
An orbital period of 3,420.000 days
Semi-major axis 4.8500 AU
Distance from Earth 240.17 light-years
Earth Similarity Index 0.293
Travel time at Voyager 1 speed 4,235,367 years

HD 128717 b Planet Profile

Physical Specs

Radius

12.10 R⊕

Radius (Jupiter)

1.080 R♃

Mass

6,293.00 M⊕

Mass (Jupiter)

19.800 M♃

Density

19.50 g/cm³

Surface Gravity

42.98 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.293

HZ Position Unknown

Controversial No

Discovery

Year 2025

Method Astrometry

Facility European Space Agency (ESA) Gaia Satellite

Telescope 1.45 m x 0.5 m Telescope

Size rank in cohort

Rank by radius

#1454of 1771

top 82.0%

This planet

12.10R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

HD 62364 b 12.10 R⊕ HD 106515 A b 12.10 R⊕ BD+20 2457 b 12.10 R⊕

Metric	Earth	HD 128717 b	Jupiter
Radius (R⊕)	1.00	12.10	11.21
Mass (M⊕)	1.00	6,293.00	317.83
Density (g/cm³)	5.51	19.50	1.33
Surface Gravity (g)	1.00	42.98	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	6,293.002 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HD 128717

HIP

HIP 71425

TIC

TIC 298163592

Gaia DR2

Gaia DR2 1610837178107032192

Gaia DR3

Gaia DR3 1610837178107032192

System

HD 128717

Percentile among Gas Giant cohort

Radius 12.100 R⊕ · percentile 16 / cohort 1771

Mass 6,293.002 M⊕ · percentile 96 / cohort 1747

Orbital period 3,420.00 d · percentile 89 / cohort 1533

Distance 73.64 pc · percentile 29 / cohort 1759

ESI 0.293 · percentile 56 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

3,420.000 days

Semi-major axis

4.8500 AU

Eccentricity

0.850

Inclination

130.30 °

Year Length

A year here lasts about 9.36 Earth years on a highly eccentric trajectory at a mean orbital distance of 4.8500 AU.

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.293

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

Pinamonti et al. 2025

Instrument

Gaia CCD array

Publication

2025-12

Observation locale

Space

Discovery cohort

Planets confirmed in 2025 at European Space Agency (ESA) Gaia Satellite (2 shown).

Gaia-4 b · Gas Giant Gaia-5 b · Gas Giant

Host System: HD 128717

Spectral Class

F-type yellow-white

Effective Temperature

6,210 K — hotter than the Sun (5,778 K)

Estimated Age

1.40 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.248 R☉

Stellar Mass

1.212 M☉

Metallicity [Fe/H]

0.16

Extended Stellar Properties

Surface gravity (log g)

4.329 dex

Stellar density

0.879 g/cm³

Rotational v·sin i

6.10 km/s

Activity index (log R'HK)

-4.948

Metallicity ratio

[Fe/H]

Distance

73.64 parsec

Light-years 240.17 ly

V-band magnitude

8.32 mag

Voyager-speed travel 4,235,367 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

13.551 mas

Total Proper Motion

105.912 mas/yr

PM Right Ascension

-82.04 mas/yr

PM Declination

66.99 mas/yr

Galactic Cartesian (pc)

x = -0.416 · y = -0.338 · z = 0.844

Equatorial (J2000)

RA 219.08817° · Dec 57.56095°

Galactic ℓ, b

98.902° · 54.397°

Ecliptic λ, β

176.504° · 65.347°

HTM-20 index

1710538456