Are you an EPFL student looking for a semester project?
Work with us on data science and visualisation projects, and deploy your project as an app on top of Graph Search.
Concept
Hypergiant
Summary
A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classifications. Astronomers are interested in these stars because they relate to understanding stellar evolution, especially star formation, stability, and their expected demise as supernovae.
In 1956, the astronomers Feast and Thackeray used the term super-supergiant (later changed into hypergiant) for stars with an absolute magnitude brighter than MV = −7 (MBol will be larger for very cool and very hot stars, for example at least −9.7 for a B0 hypergiant). In 1971, Keenan suggested that the term would be used only for supergiants showing at least one broad emission component in Hα, indicating an extended stellar atmosphere or a relatively large mass loss rate. The Keenan criterion is the one most commonly used by scientists today.
To be classified as a hypergiant, a star must be highly luminous and have spectral signatures showing atmospheric instability and high mass loss. Hence it is possible for a non-hypergiant, supergiant star to have the same or higher luminosity as a hypergiant of the same spectral class. Hypergiants are expected to have a characteristic broadening and red-shifting of their spectral lines, producing a distinctive spectral shape known as a . The use of hydrogen emission lines is not helpful for defining the coolest hypergiants, and these are largely classified by luminosity since mass loss is almost inevitable for the class.
Stars with an initial mass above about quickly move away from the main sequence and increase somewhat in luminosity to become blue supergiants.
Official source
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.