Astronomers find the 'roundest' star in the universe

Stars are not perfect spheres. While they rotate, they become flat due to the centrifugal force. Researchers around Laurent Gizon from the Max Planck Institute for Solar System Research and the University of Göttingen have succeeded in measuring the oblateness of a slowly rotating star with unprecedented precision.

The researchers have determined stellar oblateness using asteroseismology - the study of the oscillations of stars. The technique is applied to a star 5000 light years away from Earth and revealed that the difference between the equatorial and polar radii of the star is only 3 kilometers - a number that is astonishing small compared to the star's mean radius of 1.5 million kilometers; which means that the gas sphere is astonishingly round.

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 km larger than at the poles; for the Earth this difference is 21 km. 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. The periodic expansions and contractions of the star can be detected in the fluctuations in brightness of the star.

To read more about the research and other findings, click here.