XO-3b - Orbital Inclination

Orbital Inclination

Measurements of the Rossiter-McLaughlin effect allow a determination of the angle between the planet's orbital plane and the equator of the parent star. Initial reports suggested this angle was very large, at 70 ± 15 degrees, which is significantly larger than that of the other transiting planets for which this measurement has been made. The authors cautioned that systematic effects may have affected the measurements, and a later determination by an independent group of astronomers determined a reduced value of 37.3 ± 3.7 degrees. This value is however still larger than the misalignment between the Sun's equator and the orbital plane of Jupiter, which is only 6°.

The misalignment may indicate that in the past an encounter with another planet altered its orbit, kicking it out of the plane of the planetary system. Another planetary system that may have also undergone such planet-planet interactions is Upsilon Andromedae.