About this world
HD 278555 b is a gas giant orbiting HD 278555, a yellow-white F-type star (type F8) 945 light-years from Earth. It is about 0.98 times the size of Jupiter and holds 0.84 Jupiter masses. It completes an orbit every 28.8 days at 0.2 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 853 K (580 °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 2026 by transit with Transiting Exoplanet Survey Satellite (TESS). A planet crosses its star and dims it by a tiny, periodic fraction.