About this world
HD 128717 b is a gas giant orbiting HD 128717, a yellow-white F-type star 240 light-years from Earth. It is about 1.1 times the size of Jupiter (its size estimated from its mass) and holds 20 Jupiter masses. It completes an orbit every 9.36 years at 4.8 AU from its star, on a strongly elongated orbit (e = 0.85).
Its equilibrium temperature is about 152 K (−121 °C): too cold for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 2025 by other methods with European Space Agency (ESA) Gaia Satellite. Astrometry, orbital brightness modulation and disk kinematics.