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.
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, 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.
|<< 8. KY Cygni||9. HR 5171||10. Mu Cephei >>|
Yellow Evolutionary VoidThe 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.
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).
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.
- ↑ http://adsabs.harvard.edu/doi/10.1086/191373
- ↑ 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
- ↑ 3.0 3.1 3.2 https://www.aanda.org/articles/aa/abs/2017/10/aa31569-17/aa31569-17.html
- ↑ 4.0 4.1 4.2 https://www.aanda.org/articles/aa/abs/2017/01/aa29349-16/aa29349-16.html
- ↑ http://iopscience.iop.org/article/10.1088/0004-637X/697/1/133/meta
- ↑ https://www.aanda.org/articles/aa/abs/2011/10/aa17521-11/aa17521-11.html