- Yellow hypergiant
Generally speaking, a yellow hypergiant is a very massive
starwith an extended atmosphere, which can be classified as spectral class from late A to K, with a mass of as much as 20-50 solar masses. Yellow hypergiants, such as Rho Cassiopeiaein 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 sequencefor a few million years before destroying themselves in a massive supernovaor hypernova.
According to 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.
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 have very large, extended atmospheres. A disk of dust and gas can also sometimes be identified, allowing the possibility of planetary systems around these stars.
Known yellow hypergiants
* [http://www.aas.org/publications/baas/v34n4/aas201/1007.htm "The Millennium Outburst of the Star Rho Cassiopeiae"]
* Seeds, Michael A., "Astronomy: The Solar System and Beyond", Brooks/Cole 2005.
* [http://arxiv.org/abs/astro-ph/0407202 arXiv.org>astro-ph>0407202] explanation on YHG:s as a missing LBV link.
Wikimedia Foundation. 2010.
Look at other dictionaries:
Hypergiant — A hypergiant (luminosity class 0) is a star with a tremendous mass and luminosity, showing signs of a very high rate of mass loss. CharacteristicsThe word “hypergiant” is commonly used as a loose term for the most massive stars found, even though … Wikipedia
Yellow supergiant — A yellow supergiant (YSG) is a supergiant star of spectral type F or G. [p. 366, The evolution of massive stars with mass loss, Cesare Chiosi and Andre Maeder, Annual review of astronomy and astrophysics 24 (1986), pp. 329 ndash;375.… … Wikipedia
Stellar classification — In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are… … Wikipedia
Hypernova — For the rock band, see Hypernova (band). Eta Carinae, in the constellation of Carina, one of the nearer candidates for a future hypernova Hypernova (pl. hypernovae), also known as a type 1c Supernova, refers to an incredibly large star that… … Wikipedia
Outline of astronomy — Mauna Kea in Hawaii is one of the world s premier observatory sites. Pictured is the W. M. Keck Observatory, an optical interferometer. The following outline is provided as an overview of and topical guide to astronomy: Astronomy – studies the… … Wikipedia
Supernova — This article is about the astronomical event. For other uses, see Supernova (disambiguation). Multiwavelength X ray, infrared, and optical compilation image of Kepler s supernova remnant, SN 1604. A supernova is a stellar explosion that is more… … Wikipedia
List of most massive stars — This is a list of the most massive stars so far discovered. The list is ordered by solar mass (1 solar mass = the mass of Earth s Sun). Stellar mass is the most important attribute of a star. Combined with chemical compositions, mass determines a … Wikipedia
Giant star — Hertzsprung–Russell Diagram Spectral Type Bro … Wikipedia
Neutron star — redirects here. For the story by Larry Niven, see Neutron Star (short story). Neutron stars crush half a million times more mass than Earth into a sphere no larger than Manhattan. A neutron star is a type of stellar remnant that can result from… … Wikipedia
Magnetar — For the hedge fund, see Magnetar Capital. Artist s conception of a magnetar, with magnetic field lines A magnetar is a type of neutron star with an extremely powerful magnetic field, the decay of which powers the emission of copious amounts of… … Wikipedia