About this world
HD 1397 b is a gas giant orbiting HD 1397, a yellow, Sun-like star (type G5III/I) 260 light-years from Earth. It is about 1 times the size of Jupiter and holds 0.42 Jupiter masses. It completes an orbit every 11.5 days at 0.11 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.25).
Its equilibrium temperature is about 1,228 K (955 °C): far too hot for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 2018 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction.