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1 known planet · 240.2 light years

HD 128717

HD 128717 is a white star 240.2 light years away, with 1 confirmed planet. Distances and orbital speeds are to scale; the star and planets are enlarged so you can see them.

Day 0
habitable zone (estimate)planet orbits

Green band: where liquid water could exist on a planet's surface. Drag to turn the system, pinch or scroll to zoom.

The star

The star

HD 128717

Type
white star
Surface
≈ 6,210 K
Size
1.25 × the Sun
Mass
1.21 × the Sun
Brightness
2.1 × the Sun
Habitable zone
1.06–2.47 AU

The planets

HD 128717

HD 128717 b

Year
9.4 years
Distance from star
4.85 AU
Mass
20 Jupiters
Size
12 × Earth
Temperature
≈ 152 K (-121 °C)
Found
2025, astrometry (European Space Agency (ESA) Gaia Satellite)
Outside the habitable zone

Masses found by the wobble method are minimums, because the orbit's tilt is unknown. Temperatures are equilibrium estimates for a bare planet, before any atmosphere.

How we know

The star's drift

The planet pulls the star in a tiny loop across the sky, measured against background stars over many years.

Sources

  1. Planet and star parameters: NASA Exoplanet Archive, Planetary Systems Composite Parameters, retrieved 1 Nov 2026. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.
  2. Position: HYG Database v4.1 (CC BY-SA 4.0).
  3. Habitable zone: a simple estimate from the star's brightness (√L × 0.95 to 1.67 AU), shown as a guide.
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