About this world
HAT-P-9 b is a gas giant orbiting HAT-P-9, a yellow-white F-type star (type F7) 1.48 thousand light-years from Earth. It is about 1.4 times the size of Jupiter and holds 0.75 Jupiter masses. It completes an orbit every 3.92 days at 0.053 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,540 K (1,267 °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 2008 by transit with HATNet. A planet crosses its star and dims it by a tiny, periodic fraction.