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'''Hypergiant stars''' are the brightest and most massive [[star]]s known.<ref name=universetoday>{{cite web|url=https://www.universetoday.com/25176/hypergiant-stars/|title=Hypergiant stars|accessdate=2019-03-21}}</ref> Although the term is used loosely, the criterion used to separate [[supergiant]]s from hypergiants is that the latter are stars with an [[star magnitude|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.<ref>de Jager, C. (1998). The yellow hypergiants. ''Astronomy and Astrophysics Review'', 8(3), pp.145-180. [https://ui.adsabs.harvard.edu/#abs/1998A&ARv...8..145D/abstract Bibcode: 1998A&ARv...8..145D]</ref> Like supergiants, these most luminous of stars can have a [[spectral type]] ranging from class A to M.

'''Hypergiant stars''' are the brightest and most massive [[star]]s known.<ref name=universetoday>{{cite web|url=https://www.universetoday.com/25176/hypergiant-stars/|title=Hypergiant stars|accessdate=2019-03-21}}</ref> Although the term is used loosely, the criterion used to separate [[supergiant]]s from hypergiants is that the latter are stars with an [[star magnitude|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.<ref>de Jager, C. (1998). The yellow hypergiants. ''Astronomy and Astrophysics Review'', 8(3), pp.145-180. [https://ui.adsabs.harvard.edu/#abs/1998A&ARv...8..145D/abstract Bibcode: 1998A&ARv...8..145D]</ref> 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'''. 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.<ref name=universetoday/>

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'''.<ref>{{cite web|url=https://www.britannica.com/science/Eddington-mass-limit|title=Eddington mass limit|accessdate=2019-03-31}}</ref> 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.<ref name=universetoday/>

An example of a red hypergiant is [[VY Canis Majoris]].<ref name=universetoday/> It is thought to be 1,420 times the radius of the [[Sun]].<ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/vy-canis-majoris/|title=VY Canis Majoris|accessdate=2019-03-27}}</ref> 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.<ref name=constellation-guide/> This class of star also includes [[Eta Carinae]], one of the alrgest known stars.<ref>{{cite web|url=https://www.constellation-guide.com/eta-carinae/|title=Eta Carinae|accessdate=2019-03-31}}</ref> A [[binary star|binary system]], the blue hypergiant has a mass of over 90 [[solar mass]]es, with the smaller one 30.<ref>{{cite web|url=https://www.nasa.gov/content/goddard/nasa-observatories-take-an-unprecedented-look-into-superstar-eta-carinae|title=NASA Observatories Take an Unprecedented Look into Superstar Eta Carinae|accessdate=2019-03-31}}</ref>

An example of a red hypergiant is [[VY Canis Majoris]].<ref name=universetoday/> It is thought to be 1,420 times the radius of the [[Sun]].<ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/vy-canis-majoris/|title=VY Canis Majoris|accessdate=2019-03-27}}</ref> 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.<ref name=constellation-guide/> This class of star also includes [[Eta Carinae]], one of the alrgest known stars.<ref>{{cite web|url=https://www.constellation-guide.com/eta-carinae/|title=Eta Carinae|accessdate=2019-03-31}}</ref> A [[binary star|binary system]], the blue hypergiant has a mass of over 90 [[solar mass]]es, with the smaller one 30.<ref>{{cite web|url=https://www.nasa.gov/content/goddard/nasa-observatories-take-an-unprecedented-look-into-superstar-eta-carinae|title=NASA Observatories Take an Unprecedented Look into Superstar Eta Carinae|accessdate=2019-03-31}}</ref>