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1,300 times bigger than Sun: Largest yellow ‘hyper-giant’ star identified

Published time: March 14, 2014 09:02
Edited time: March 16, 2014 10:15
HR 5171, the brightest star just below the centre of this wide-field image, which is a yellow hypergiant, a very rare type of stars with only a dozen known in our galaxy. (AFP Photo / ESO / Digitized Sky Survey 2)

HR 5171, the brightest star just below the centre of this wide-field image, which is a yellow hypergiant, a very rare type of stars with only a dozen known in our galaxy. (AFP Photo / ESO / Digitized Sky Survey 2)

Astronomers have identified the largest ‘yellow’ star ever observed in our galaxy and one of the 10 largest ever discovered in total. The star is more than 1,300 times the diameter of the sun and 1,000,000 times brighter.

The star named HR 5171 A is 12,000 light-years from Earth and can even be seen with the naked eye. It was discovered by an international team of scientists using the European Space Organization’s Very Large Telescope Interferometer in Paranal, Chile.

Yellow hypergiants are extremely rare; approximately a dozen are known to exist in the Milky Way. In general, they are very unstable because of the stage of their ‘life’. The most well-known is Rho Cassiopeiae in the Cassiopeia constellation.

HR 5171 A is also 50 times bigger than red supergiant Betelgeuse in the Orion constellation.

The size of the star took the group of scientists by surprise, given their earlier observations. The work of Olivier Chesneau and his team is to be published in the journal Astronomy & Astrophysics.

Astronomers made a further surprising discovery about the star.

“The new observations also showed that this star has a very close binary partner, which was a real surprise,” said Chesneau from the Observatoire de la Côte d’Azur in Nice, France. “The two stars are so close that they touch and the whole system resembles a gigantic peanut.”

HR 5171 A is orbited by this companion – which is slightly hotter than the 5000 degrees Celsius (surface temperature) hypergiant – 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 in a press release on the ESA’s website.

The process of discovery was made using a method called interferometry, which collects and combines light from multiple telescopes, creating one new massive telescope.

Researchers collated data from past decades, noting that the star has been changing rapidly over the time period too. It has been increasing in size over the past 40 years and cooling down as it grows.

Comments (11)


eyeofinsight 14.03.2014 22:31

BillBo 14.03.2014 13:00

It makes perfect sense if you can read/comprehend the article correctly. It was IDENTIFIED, not "discovered.&am p;amp;qu ot;

Our ancient ancestors could see many stars with the naked eye, doesn't mean they really knew anything about them.


Ye ah, but he article clearly says ''discovered'' and not identified. You are being facetious and playing semantics. In case you are mistaken about about the meaning of discovered-to see, find, gain sight (something previously unseen). There you go.


nick 14.03.2014 17:06

Vlada 14.03.2014 11:54

Such a large star rapidly changing might not be a good news for us, particularly given its relatively close proximity to Earth. The rapidly changing phase means it is going into a supernovae soon, that is, exploding and subsequently cooling maybe even into a black hole (or a neutron star). Not only we have a looming worldwide political turmoil (a war?), but now that star is going to make a mess.


Bear in mind that we are seeing it as it was 12000 years ago. If it was heading towards supernova then, it may well no longer exist.


nick 14.03.2014 17:02

"1300 times bigger than the sun" is very different from "1300 times the diameter of the sun". So which is it?

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