A group of astronomers from around the world have discovered that the star KIC 11145123 is the roundest object in the universe, with a difference of only 3 kilometers (2 miles) between its polar and equatorial radius, which are about 1,558,000 kilometers (968,300 miles) apart. Pretty good for a star 5,000 light-years away.
The team, led by Professor Laurent Gizon from the Max Plank Institute for Solar System Research, discovered the extreme roundness of this star by studying the interior oscillations of the star.The results are published in Science Advances.
The technique is called asteroseismology, and like seismology helps geologists understand the interior of our planet, this astronomical approach has allowed researchers to work out what’s going on under the surface of distant stars. The star was continuously observed by NASA’s Kepler mission for four years, which allowed the team to work out how the star’s oscillation affected its light.
“The periodic expansions and contractions of the star can be detected in the fluctuations in brightness of the star,” Professor Gizon told IFLScience. “The frequencies of the modes of oscillation can inform us about the mean stellar density, the age of the star, and the rotation of the star. What is new in this paper is that we use the frequencies of the modes of oscillations to learn about the shape of stars.”
In the paper, the researchers explain that the star rotates very slowly, which is one of the reasons why the star is so round. A star is a big ball
of plasma and its rotation, magnetic field, and other factors are responsible for the final shape of the object.
KIC 11145123 was selected because it has very long-lived oscillations that the team was able to measure with ground-breaking precision.
KIC11145123 compared to the Sun. The oblateness of the Sun is exaggerated 10,000 times. Laurent Gizon et al. and the Max Planck Institute for Solar System Research, Germany. Illustration by Mark A. Garlick.
“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,” added Gizon. “It will be particularly interesting to see how a faster rotation and a stronger magnetic field can change a star’s shape. An important theoretical field in astrophysics has now become observational.”
Asteroseismology has become an important technique in the last few years, allowing astronomers to look inside stars. With the right instruments, it might soon reveal a lot more.