March 12, 2014
Astronomers Discover Hypergiant Star 1300 Times The Size Of Our Sun
[ Watch the Video: Artist's Impression of Yellow Hypergiant Star HR 5171 ]
Lee Rannals for redOrbit.com - Your Universe Online
Astronomers using the European Southern Observatory’s (ESO) Very Large Telescope have discovered the largest yellow star so far.
The team discovered yellow hypergiant star HR 5171 in a double star system about 12,000 light-years away from Earth. The star is so huge that it can just about be seen with the naked eye, despite its distance from Earth.
“The new observations also showed that this star has a very close binary partner, which was a real surprise,” Olivier Chesneau, from the Observatoire de la Côte d’Azur, Nice, France, said in a statement. “The two stars are so close that they touch and the whole system resembles a gigantic peanut.”
The astronomers used a technique known as interferometry, combining light collected from multiple individual telescopes to essentially create a giant telescope. They were able to use these results to investigate older observations of the star spanning more than sixty years in order to see how it behaved.
Yellow hypergiants are considered rare, and only a dozen of the colossal stars have been discovered in the Milky Way galaxy. This star class is among the biggest and brightest stars known and are at a stage of their lives when they are unstable and changing rapidly.
“This new discovery highlights the importance of studying these huge and short-lived yellow hypergiants, and could provide a means of understanding the evolutionary processes of massive stars in general,” ESO said in a statement.
HR 5171 is 1300 times the diameter of the Sun, making it the largest yellow star known to exist. The star is also ranked in the top 10 of the largest known stars and is 50 percent larger than the famous red supergiant Betelgeuse.
The astronomers say that HR 5171 has been getting bigger over the past 40 years and is cooling as it grows. Only a few stars have been observed in this phase where they begin to undergo a dramatic temperature change.
The scientists analyzed data on the star’s varying brightness and used observations from several observatories to confirm that the star is an eclipsing binary system. They found that HR 5171 is being orbited by its companion star every 1,300 days.
“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.
The astronomers reported their findings in the journal Astronomy & Astrophysics.
Image Below: HR 5171, the brightest star just below the centre of this wide-field image, is a yellow hypergiant, a very rare type of stars with only a dozen known in our galaxy. Its size is over 1300 times that of the Sun — one of the ten largest stars found so far. Observations with ESO’s Very Large Telescope Interferometer have shown that it is actually a double star, with the companion in contact with the main star. Credit: ESO/Digitized Sky Survey 2