All stars rotate and are therefore flattened by the centrifugal force. The faster the rotation, the more oblate the star becomes. Our Sun rotates with a period of 27 days and has a radius at the equator that is 10 kilometres larger than at the poles; for the Earth this difference is 21 kilometres. Gizon and his colleagues selected a slowly rotating star named Kepler 11145123. This hot and luminous star is more than twice the size of the Sun and rotates three times more slowly than the Sun.
Surprisingly, the star is even less oblate than implied by its rotation rate. The authors propose that the presence of a magnetic field at low latitudes could make the star look more spherical to the stellar oscillations. Just like helioseismology can be used to study the Sun’s magnetic field, asteroseismology can be used to study magnetism on distant stars. Stellar magnetic fields, especially weak magnetic fields, are notoriously difficult to directly observe on distant stars.
Kepler 11145123 is not the only star with suitable oscillations and precise brightness measurements. “We intend to apply this method to other stars observed by Kepler and the upcoming space missions TESS and PLATO. It will be particularly interesting to see how faster rotation and a stronger magnetic field can change a star’s shape,” Gizon adds, “An important theoretical field in astrophysics has now become observational.”
NASA’s Kepler mission has verified 1,284 new planets — the single largest finding of planets to date. Of the nearly 5,000 total planet candidates found to date, more than 3,200 now have been verified, and 2,325 of these were discovered by the space telescope. Launched in March 2009, Kepler is the first NASA mission to find potentially habitable Earth-size planets.
NASA’s new planet-hunting TESS observatory completed its first post-launch thruster firing Saturday, setting up for a big boost Wednesday that will send the spacecraft toward the moon for a flyby next month, the next maneuvers in a two-month process to reach the mission’s final science orbit in mid-June.
A group of researchers has observed the first ground-based transit observation of K2-3d — a potentially Earth-like extrasolar planet supposedly within the habitable zone around a bright M-dwarf host star 147 light-years away — using the multi-band imager MuSCAT on the Okayama Astrophysical Observatory’s 1.88-metre telescope.