Last modified on 31 March 2019, at 15:43

Hypergiant

Hypergiant stars are the brightest and most massive stars known.[1] Although the term is used loosely, the criterion used to separate supergiants from hypergiants is that the latter are stars with an absolute magnitude greater than -7. Because of this, hypergiants do not have to be the more massive than other supergiants, but the most massive stars are still generally seen as hypergiants.[2] Like supergiants, these most luminous of stars can have a spectral type ranging from class A to M.

Hypergiants are so luminous that they sit very close to the point where radiation from the interior of the star would overcome the inward force of gravity. This theoretical upper limit for the luminosity of a star is called the Eddington limit.[3] Any star that exceeds this limit will be blown apart from its own immense radiation. This leads to the star ejecting large amounts of mass. They have luminosities millions of times greater than the Sun's.[1]

An example of a red hypergiant is VY Canis Majoris.[1] It is thought to be 1,420 times the radius of the Sun.[4] Sitting near the Eddington limit, it looses mass at a rate 270,000 times that of the Sun, equivalent to 30 times the mass of the Earth every year.[4] This class of star also includes Eta Carinae, one of the alrgest known stars.[5] A binary system, the blue hypergiant has a mass of over 90 solar masses, with the smaller one 30.[6]

References

  1. 1.0 1.1 1.2 Hypergiant stars. Retrieved on 2019-03-21.
  2. de Jager, C. (1998). The yellow hypergiants. Astronomy and Astrophysics Review, 8(3), pp.145-180. Bibcode: 1998A&ARv...8..145D
  3. Eddington mass limit. Retrieved on 2019-03-31.
  4. 4.0 4.1 VY Canis Majoris. Retrieved on 2019-03-27.
  5. Eta Carinae. Retrieved on 2019-03-31.
  6. NASA Observatories Take an Unprecedented Look into Superstar Eta Carinae. Retrieved on 2019-03-31.