Researchers at the Max Planck Institute for Solar System Research and the University of Gottingen have found the roundest object in the universe: a distant star named Kepler 11145123, located around 5,000 light-years away from Earth.
The Kepler star is much larger than the sun, and is also much closer to a perfect spherical shape, Tech Times reports.
Stars and planets are not round. Because of centrifugal force, celestial objects flatten out in the middle, kind of like a disc. The faster planets or stars spin, the greater the centrifugal force, and the flatter the object gets flatter.
To find out how flat an object is, astronomers compute the difference between an object’s polar and equatorial radii. The sun, which makes one complete rotation every 27 Earth days, has a difference of 10 kilometers, while the Earth has a difference of 21 kilometers.
The team, led by Laurent Gizon, used a technique called asteroseismology, which studies how a star oscillates. They found that the Kepler 11145123 star only has a difference of 3 kilometers – a number that is incredibly small relative to the star’s mean radius of 1.5 kilometers. This indicates that the star is very round.
Gizon says,
This makes Kepler 11145123 the roundest natural object ever measured, even more round than the sun.
Astronomers studied the star’s activity for four years, and found that it had two oscillation modes individually oriented with different latitudes. The difference in frequency shifts during the two oscillations revealed the star’s radii measurements.
The scientists on the study think that the low-altitude magnetic field of the star might be responsible for the star’s roundness. The radii differences may also be used to study magnetism on other stars. The authors wrote, “Because the observed ΔR/R is only one-third of the expected rotational oblateness, we conjecture the presence of a weak magnetic field on a star that does not have an extended convective envelope.”
Gizon’s team said they intend to use the method to study Kepler 11145123 on other stars that are observed by the Kepler space telescope and other space missions.
The study was published in Science Advances.
