About this world
XO-3 b is a gas giant orbiting XO-3, a yellow-white F-type star (type F5V) 695 light-years from Earth. It is about 1.3 times the size of Jupiter and holds 13 Jupiter masses. It completes an orbit every 3.19 days at 0.048 AU from its star, closer than Mercury is to the Sun, on a strongly elongated orbit (e = 0.28).
Its equilibrium temperature is about 1,890 K (1,617 °C): far too hot for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium. Its atmosphere has already been studied: 22 spectroscopic observations.
It was discovered in 2007 by transit with XO. A planet crosses its star and dims it by a tiny, periodic fraction.