Exoplanet · gas giant
HD 128717 b
HD 128717 b is a gas giant orbiting the star HD 128717. Its year lasts 3,420 Earth days. It was discovered in 2025 by the Astrometry method.
| Host star | HD 128717 |
|---|---|
| Distance | 240.2 light-years (73.6 pc) |
| Orbital period | 9.36 years |
| Orbital radius | 4.85 AU |
| Eccentricity | 0.850 |
| Radius | 12.1 R⊕ · 1.08 R♃ |
| Mass | 6,290 M⊕ · 19.8 M♃ |
| Density | 19.5 g/cm³ |
| Surface gravity | 43 × Earth |
| Equilibrium temperature | 152 K (-121 °C) |
| Stellar flux received | 0.0892 × Earth |
| Discovery method | Astrometry |
| Discovery year | 2025 |
| Discovered by | European Space Agency (ESA) Gaia Satellite |
Habitable zone
Beyond the habitable zone: it receives only %8.9 of the light the Earth does, a frozen world.
Its star in the sky
In the planet's sky its star is a disc 0.14° across: 0.26 times the Sun as we see it from Earth.
In the sky
Too faint for the naked eye (magnitude 8.32); binoculars will find it. Visible from the whole Northern Hemisphere and south to latitude 32° S. North of latitude 32° N it never sets. It stands highest at midnight in April, the best time to observe it.
Light's journey
The light you see tonight set out around the year 1786. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 4.3 million years.
Data: NASA Exoplanet Archive, PSCompPars. Its look in the simulation is a rendering based on the measured radius, mass and temperature.