Kepler finds system with planets sharing extremely tilted orbital plane

Nature : The planets in our solar system all orbit in the same direction and in the same plane, which is just 7.2° off the Sun’s equator. Many of the exoplanets found in recent years, however, have been discovered to orbit at steep angles to their parent star’s equator. Until now, no one had seen an entire solar system of planets all sharing the same extremely tilted orbital plane. Kepler-56 is a star with a diameter four times that of the Sun. Located 2800 light-years away, it has two known planets that lie on the same orbital plane and have orbital distances smaller than Mercury’s. Daniel Huber of NASA’s Ames Research Center in Moffett Field, California, and his colleagues studied variations in the star’s brightness, which are caused by stellar vibrations. Their observations revealed that the plane of the star’s equator is at a 45° angle to the plane of the planetary orbits. Further observations using the 10-m Keck telescope on Mauna Kea in Hawaii to determine the motion of the star through space revealed a distant object pulling on the star and also pulling the planets into their skewed plane. Additionally, the two planets have resonant orbits—the outer planet has twice the orbital period as the inner—which helps keep them aligned.