Astronomers Find Largest Yellow Hypergiant Star

Posted on March 12, 2014

Artists impression yellow hypergiant star HR 5171

Astronomers using ESO's Very Large Telescope have found the largest yellow hypergiant star. HR 5171 A has 1300 times the diameter of the Sun and it is about one million times brighter than the Sun. The star is also in the top ten of the largest stars known. It is 50% bigger than the red supergiant Betelgeuse. The enormous star has another star next to it in the double star system.

Olivier Chesneau from the Observatoire de la Côte d'Azur in Nice, France led the international team of astronomers. He compares the system to a giant peanut. Chesneau says, "The new observations also showed that this star has a very close binary partner, which was a real surprise. The two stars are so close that they touch and the whole system resembles a gigantic peanut."

The astronomers say HR 5171 A has been getting bigger over the past 40 years and is cooling as it grows. They also say HR 5171 A is so huge it can almost be seen with the naked eye despite being nearly 12,000 light-years away from Earth.

A research paper, "The yellow hypergiant HR 5171 A: Resolving a massive interacting binary in the common envelope phase," was published here in the journal, Astronomy & Astrophysics.

The image below shows the field around HR 5171.

HR 5171 wide field image

Image: ESO (top)/ESO/Digitized Sky Survey 2 (second)