Using the Very Large Telescope, scientists have discovered a hypergiant star is actually the largest yellow star ever found. HR 5171 is one of the largest starts ever discovered! It’s even 50 percent larger than the famous red supergiant, Betelgeuse.
Scientists and amateur observers have been watching the yellow hypergiant star HR 5171 A for more than 60 years. Using the European Southern Observatory’s Very Large Telescope Interferometer, an international team of researchers have discovered that the yellow hypergiant is even bigger than expected: It’s 1,300 times the diameter of the Sun and about a million times brighter. Doing simple calculations, we see that the radius would of HR 5171is 904,150,000 km, which is approximately 6.04 AU. The distance from the Sun to Jupiter is 5.2 AU, so that means that if HR 5171 was at the center of our solar system it would reach somewhere in between Jupiter and Saturn!
Only about a dozen of these yellow hypergiants are known in our galaxy, for example Rho Cassiopeiae. They are some of the biggest, brightest stars, and we are seeing them while they are unstable and rapidly changing stage of their lives. This one was found during a very short-lived phase. HR5171 is a massive interacting binary star, which is a double-star system where both stars are still in contact.
Although its is nearly 12,000 light years away from Earth, it is visible to the naked eye. It can be found in the constellation Centaurus.
http://www.eso.org/public/news/eso1409/
http://rt.com/news/sun-yellow-star-biggest-622/
http://en.wikipedia.org/wiki/Interacting_binary_star
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