Astronomers this week revealed that they have spotted the largest yellow star ever seen. The object is more than 1300 times the diameter of our Sun and is also one million times brighter. It is also one of the ten largest stars ever discovered. The new observations are to be published in the journal Astronomy & Physics.

The star is located around 12,000 light-years from our solar system and has been designated HR 5171 A. The discovery was made using the Very Large Telescope array in Chile.

HR 5171 A is even more unique due to being part of a binary star system. The new observations show that the star is so large that it and its partner star are actually touching.

“The new observations also showed that this star has a very close binary partner, which was a real surprise,” said Olivier Chesneau, lead author of the paper and an Astronomer at the Observatoire de la Côte d’Azur. “The two stars are so close that they touch and the whole system resembles a gigantic peanut.”

HR 5171 A is one of a very rare group of stars that astronomers refer to as yellow “hypergiants.” The largest of stars are more commonly red or blue in color. According to researchers,the yellow hypergiants are rare because they represent a quickly-passing phase in the life of some stars that are both unstable and undergoing rapid changes. In this case, HR 5171 A is cooling as its companion star strips off the star’s outer layers.

“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,” said Chesneau.

Image via ESO