Measuring the Shape of Stars - Universe Today
The faster a star spins, the more it flattens out, changing from a sphere to something more egg-shaped. Since stars are points of light in the sky, it's difficult to determine their shape, but astronomers are now using gravitational lensing to get a sense of the shape of stars. This depends on the light from a distant star being deflected by the gravity of something closer. In a recent lensing event, where a closer star eclipsed a more distant star, astronomers were able to detect that the background star was slightly elongated. This is impressive considering the distant star was 16,000 light-years away.