Hypergiant Star Discovered, One of the Largest Ever

Hypergiant

A giant yellow star, also known as a hypergiant, was spotted and is one of the largest objects ever discovered in the universe by astronomers. The star is called HR 5171 and it is brighter than the sun by the millions when considering how many times. It also has a diameter 1300 times the center star of this solar system we live in. The surface temperature of HR 5171 is 5,000 degree Celsius or in Fahrenheit, 9032 degrees.

HR 5171 is also known as HD 119796, HIP 67261, and V766 and it was discovered by the Very Large Telescope by a group known as the European Southern Observatory. The research was led by Olivier Chesneau from a French observatory and was published in the journal Astronomy & Astrophysics.

HR 5161 was expected to be bigger. It was estimated to be 400 to 700 times larger than the sun before it was concluded it was actually 1300 times larger. The researchers also discovered that the star has grown, to their surprise, over a 40 period year as it began to cool down.

The star is 12,000 light-years away from Earth and though it is considered one of the largest objects ever discovered, it can be seen with a naked eye. Granted, one would have to have an eye that is very sharp to see it. HR 5171 is called a hypergiant, which are stars that are considered to be very rare, with only 21 examples of them discovered. Moreover, they are very unstable and are known to be changing rapidly due to their age. This instability leads the hypergiants to form a large atmosphere around them from material they expel outwards. The most known yellow hypergiant is Rho Cassiopeiae.

Orbiting around the star is a second star so close in contact that combined they look like a ping-pong racquet. The companion star or binary partner is a surprise to the astronomers. It makes a 1300 day orbit around Hr 5171.

Their close orbit is considered to have an affect on the life-cycle of the system in regards to its dynamics. Chesneau said the partner can have a significant influence on HR 5171 as it could strip off the outer layers of the star and modify its evolution. Nevertheless, Chesneau concluded that it likely does not have any kind of effect on HR 5161 based on the research.

To observe the hypergiant was no small feat. Researchers used 60 years of VLT compiled data and various other telescopes. Observations from the past compiled onto the new observations by the VLT helped the researchers understand previous behavior of the hypergiant.

Though HR 5171 is considered one of the largest stars ever discovered, it is nowhere near the biggest of them all. The hypergiant pales in comparison to UY Scuti, a star 1708 times larger than the radius of the sun. The hypergiant, in fact, is the eighth largest ever discovered behind such stars as PZ Cassiopeiae, which is somewhere between 1,260-1,340 times larger than the radius of the sun, and AH Scorpii, which is 1,287 -1,535 times larger than the radius of the sun.  This finding by the research team is considered unique by astronomers and it could be key into understanding how stars interact.

By Kollin Lore

Sources

Discovery News
International Business Times
Daily Mail

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