Confirmed exoplanet · Database record + computed analysis
HD 128717 b
A confirmed world orbiting HD 128717, 240.2 light-years away.
A gas giant
12.10 Earth radii, Jupiter-class (Jupiter is 11.2). With 6293.0 Earth masses packed into that size, its density points to rock and iron rather than gas.
The orbit
Its year takes 3,420 Earth days (9.4 Earth years). The orbit is strongly stretched (eccentricity 0.85), so its distance from the star, and with it the climate, swings dramatically.
Temperature and starlight
Its equilibrium temperature (the airless-world estimate) is about -121 °C. It receives only 0.09 times Earth's starlight.
Its sun
Its star is hotter than the Sun (6,210 K), burning brighter and faster.
How far is that, really?
At 240 light-years, tonight's light from this system left it around the year 1785. A Voyager-speed probe would need roughly 4,249,204 years to get there.
How we found it
It was found by astrometry, which measures the star's tiny sideways drift across the sky. The discovery was announced in 2025 from European Space Agency (ESA) Gaia Satellite.
Everything above is computed from the archive’s measured values for this planet. Where a quantity is missing, the statement is omitted rather than guessed.
About this record
The measured values come from the NASA Exoplanet Archive, and any missing value has not been determined yet; the Atlas never fills gaps with guesses. More standout worlds: Proxima b, TRAPPIST-1e, K2-18 b, 55 Cancri e, and the detection methods that found them all.