This sphere is one of the roundest objects ever made. Credit: NIST
Remember modeling the solar system with styrofoam balls? Those craft-store mockups might have seemed like good representations of the rotund shape of the heavenly bodies, but the reality is that no star or planet is perfectly round.
But now, researchers may have come close to spotting an almost perfect sphere in nature, one that makes the precise curves of styrofoam balls look like misshapen blobs.
In a paper published in Science Advances researchers describe the shape of a distant star, Kepler 11145123, located 5000 light years away from Earth. The star rotates so slowly, that it isn’t flattened out by rotational forces in the same way that stars that turn faster (like our own sun) do.
Kepler 11145123; This star (to the left) is the roundest object ever observed in nature. Credit: Mark A. Garlick
The difference between the radius of the star at its poles and at its equator is only about 3 kilometers. That’s an incredible ratio for a star that’s 1.5 million kilometers across. For comparison, the difference between the Sun’s equator and poles is 10 kilometers, and the sun is about half the size of Kepler 11145123. The Earth is even more oblate, with the difference between our equator and poles clocking in at a whopping 21 kilometers.
Researchers plan to use the same technique they used to measure the shape of this star, using the Kepler space observatory to make observations on additional targets.
The Earth might look perfectly round in this image, but measurements tell us that the diameter around the center of the Earth is not the same as the diameter from pole to pole. The difference is about 21 kilometers. Credit: NASA EPIC
“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,” Laurent Gizon, an author of the study said. “An important theoretical field in astrophysics has now become observational.”
Though the star is one of the roundest objects seen in nature, there are rounder objects in existence. As a part of the Avogadro Project, an international effort to redefine the kilogram, scientists made near-perfect spheres of silicon-28 in the lab. These spheres are among the roundest objects found anywhere, varying in diameter by only 0.00035 mm with a radius of 94 mm and a mass of exactly one kilogram.