About this world
XO-1 b is a gas giant orbiting XO-1, a yellow, Sun-like star (type G1V) 533 light-years from Earth. It is about 1.1 times the size of Jupiter and holds 0.83 Jupiter masses. It completes an orbit every 3.94 days at 0.049 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,210 K (937 °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: 6 spectroscopic observations.
It was discovered in 2006 by transit with XO. A planet crosses its star and dims it by a tiny, periodic fraction.