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 - 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