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A yellow hypergiant (also known as a post-red supergiant/hypergiant), formerly a late S Doradus variable, is a star that has a spectral classification between A0 to K2. This gives them temperatures between 4,000 and 8,000 K. Yellow hypergiants are very luminous with 200,000 to 600,000-750,000 times greater than the Sun. It is a star that was once a red supergiant, but is now getting hotter and shrinking down to a luminous blue variable and then a Wolf-Rayet star. All yellow hypergiants stars are in an extremely active phase of their evolution.

This article will cover a few examples of yellow hypergiants.

Rho Cassiopeiae

RHOCAS
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Rho Cassiopeiae

Rho Cassiopeiae, also known as 7 Cassiopeiae, is the best known yellow hypergiant. It is located in the constellation Cassiopeia 8,200 light years away from Earth. It has a diameter of 450 (= 627 million km) times that of our sun, a mass of 14 and 30 times that of our sun and a temperature between 5,777 and 7,200 degrees Kelvin. It is visible to the naked eye as it has a luminosity approximately 500,000 times brighter than the Sun.

V382 Carinae

Gstar

Artist's impression of V382 Carinae

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V382 Carinae

V382 Carinae, also known as x Carinae, is the second best known yellow hypergiant. It is easily visible with the naked eye. It is located in the constellation Carina 8,900 light years away from Earth. It has a diameter of 747 (= 1.04 billion km) times that of our sun and a mass of 20 times that of our sun. It has a temperature approximately 5,866 degrees Kelvin. It is visible to the naked eye as it has a luminosity approximately 316,000 times brighter than the Sun.

HR 5171

HR 5171, also known as the "Peanut star" or V766 Centauri, is a yellow hypergiant located in the Centaurus constellation 11,700 light years away from Earth.

The star system was originally discovered by French astronomer Olivier Chesneau. However, it was later revealed to be a binary star in 2014. Both are so close to each other that the two stars are in contact.

HR 5171 A

The main component is a star named HR 5171 A. It has a diameter of $ 1,315 (= 1.83 $ billion km) times greater than the Sun, based on a distance of $ 11,700 $ light years and an angular diameter of $ 3.39 $ milliarcseconds, making it the largest known yellow hypergiant star. It has a mass $ 27 to 36 $ times that of our sun, as well as a luminosity of 630,000 to a million times that of the sun. Its temperature vary between $ 4,290 to 5,050 $ degrees Kelvin.

HR 5171 Ab

HR 5171 Ab is a small yellow hypergiant with a diameter between 401 and 650 times greater than the sun (= 558 to 905 million km), with a temperature of 4,800 to 5,200 degress Kelvin, and a small mass of only 5 times greater than the sun.

HR 5171 B

HR 5171 B, is a blue supergiant with a temperature of 26,000 Kelvin and a luminosity of 316,000 times brighter than our sun. This star is not in contact.

Gallery

See also

<< 8. KY Cygni 9. HR 5171 10. Mu Cephei >>

V509 Cassiopeiae

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V509 Cassiopeiae

V509CAS
V509 Cassiopeiae, also known as HR 8752, is also located in the constellation Cassiopeia 4,500 light years away from Earth. It has a diameter between 400 and 900 (= 557 to 1,253 million km) times that of our sun. It has a mass of 11 times that of our sun. It has a temperature between 4,000 and 8,000 degrees Kelvin. Just like Rho Cassiopeiae, it is visible to the naked eye as it has a luminosity between 200,000 and 400,000 times brighter than the Sun.

HD 179821

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HD 179821

HD 179821
HD 179821 is a yellow hypergiant star in the Aquila constellation, surrounded by a detached dust shell. It is a semi-regular variable and either a post-AGB star or what it is more likely to be, a yellow hypergiant.

Yellow Evolutionary Void

The Yellow Evolutionary Void separates yellow hypergiants from luminous blue variables, although yellow hypergiants are the hottest and luminous blue variables are the coolest, meaning they can have approximately the same temperature (between 7,500 and 10,000 K). They are sometimes considered as stars in a Pre-Luminous Blue Variable stage. This section will cover two yellow hypergiants that are near in the bounds of the Yellow Evolutionary Void.

HD 33579

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HD 33579

HD33579
HD 33579, also known as R76, is a white/yellow hypergiant located in the Large Magellanic Cloud and in the constellation Dorado 165,000 light years away from Earth. It is amoung the brightest stars in the Large Magellanic Cloud. It has a diameter 380 R (= 530 million km), a mass between 20 and 30 M. It has a temperature 7,980 degrees Kelvin. It is visible to the naked eye as it has a luminosity approximately 525,000 times brighter than the Sun.

IRC +10420

IRC10420

Size comparison with HR 5171 A

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IRC +10420

IRC+10420, also known as V1302 Aquilae, is a yellow hypergiant located in the Aquila constellation at a distance of 5,000 parsecs (= 16,300 light years) from Earth on average. Its temperature is 6,000 to 8,000 degrees Kelvin, which mean that the star has increased its own temperature into the LBV range. It has a mass 10 times that of our sun and a diameter varying between 357 and 1,342 times that of the sun (= 497 to 1,869 million km).

Gallery

IRAS 17163-3907

Fried Egg Nebula

This picture of the nebula around IRAS 17163-3907 is the best ever taken of a star in this class. Credit to European Southern Observatory

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IRAS 17163-3907

IRAS 17163-3907 (or Hen 3-1379), also known as Fried Egg Nebula, is a possible yellow hypergiant located in the constellation Scorpius at 13,000 light years away from Earth. It has a diameter of 300 to 400 R (= 417 to 557 million km), with a temperature between 7,500 to 10,000 degrees Kelvin, which mean that the star is in a pre-LBV stage. Assuming the higher temperature is true, IRAS 17163-3907 would be the hottest yellow hypergiant star. It is visible to the naked eye as it has a luminosity approximately 500,000 times brighter than the Sun.[6]

IRAS 17163-3907 has also a double dust envelope, and like VY Canis Majoris and IRC +10420, this star has ejected much of its mass off of its atmosphere, it may explode into a supernova.

External Links

The Fried Egg Nebula

References

  1. http://adsabs.harvard.edu/doi/10.1086/191373
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 https://www.aanda.org/articles/aa/abs/2014/03/aa22421-13/aa22421-13.html
  3. 3.0 3.1 3.2 https://www.aanda.org/articles/aa/abs/2017/10/aa31569-17/aa31569-17.html
  4. 4.0 4.1 4.2 https://www.aanda.org/articles/aa/abs/2017/01/aa29349-16/aa29349-16.html
  5. http://iopscience.iop.org/article/10.1088/0004-637X/697/1/133/meta
  6. https://www.aanda.org/articles/aa/abs/2011/10/aa17521-11/aa17521-11.html