Yellow hypergiant

From Wikipedia, the free encyclopedia

Generally speaking, a yellow hypergiant is a very massive star with an extended atmosphere, which can be classified as spectral Class G, with a mass of as much as 120 solar masses (believed to be the upper limit of stellar mass). Yellow hypergiants, such as Rho Cassiopeiae in the constellation Cassiopeia, have been observed to experience periodic eruptions, resulting in periodic or continuous dimming of the star, respectively. Yellow hypergiants appear to be extremely rare in the universe. Due to their extremely rapid rate of consumption of nuclear fuel, yellow hypergiants generally only remain on the main sequence for a few million years before destroying themselves in a massive supernova or hypernova.

1 Internal Structure
2 Chromosphere
3 Known Yellow Hypergiants
4 See also
5 External links
6 References

[edit] Internal Structure

According the the current physical models of stars, a yellow hypergiant should possess a convective core surrounded by a radiative zone, as opposed to a sun-sized star, which consists of a radiative core surrounded by a convective zone (Seeds 2005). Due to the extremely high pressures which exist at the core of a yellow hypergiant, portions of the core or perhaps the entire core may be composed of degenerate matter.

[edit] Chromosphere

Due to the sheer size of these stars, in addition to powerful magnetic fields and their extreme energy output, yellow hypergiants are less effective at retaining surface material than other kinds of stars. They therefore posses very large, extended atmospheres. A disk of dust and gas can also sometimes be identified, allowing the possibility of planetary systems around these stars.