Researchers have discovered the largest-known yellow star using the European Southern Observatory's Very Large Telescope.
The behemoth star is over 1,300 times the diameter of our own Sun, a European Southern Observatory (ESO) news release reported. The star, dubbed HR 5171 A, is changing rapidly and is also believed to have a twin.
"The new observations also showed that this star has a very close binary partner, which was a real surprise," Olivier Chesneau, of the Observatoire de la Côte d'Azur, said in the news release. "The two stars are so close that they touch and the whole system resembles a gigantic peanut."
To make their finding the researchers used a technique called interferometry to combine light from several telescopes, creating one giant telescope. The research team also sifted through observations made of the star over the past 60 years.
Yellow supergiants such as HR 5171 A are extremely rare; only about a dozen of these objects are known of in the Milky Way. They are the "biggest and brightest" known stars in a phase of their lives where they are changing rapidly.
During this life stage the stars are extremely unstable, causing them to expel material and form an atmosphere around themselves.
The star has been growing and simultaneously cooling down over the past four decades. Very few stars have given researchers the opportunity to witness the life stage.
The team used data on the star's "varying brightness" to determine the object was a member of an eclipsing binary system. The star is believed to be orbited by its twin every 1,300 days. The twin, dubbed HR 5171 A, is slightly smaller and hotter than HR 5171 A.
"The companion we have found is very significant as it can have an influence on the fate of HR 5171 A, for example, stripping off its outer layers and modifying its evolution," Chesneau said.
