Yellow hypergiant
Encyclopedia
Generally speaking, a yellow hypergiant is a massive star
with 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 hypergiant
s, 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
. Yellow hypergiants are post-red supergiants, rapidly evolving toward the blue supergiant
phase. They are in a so-called "Yellow Evolutionary Void," a part of the Hertzsprung-Russell diagram where post-red supergiants exhibit atmospheric instability while evolving blueward; however, there exists strong chemical and surface gravity evidence that the brightest of the yellow supergiants, HD 33579, has not yet been to the red region. They can quickly run out of core nuclear fuel and implode to become Type II supernovae.
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
.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
with an extended atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
, which can be classified as spectral class from late A to K, with a mass of as much as 20-50 solar masses. Yellow hypergiant
Hypergiant
A hypergiant is a star with a tremendous mass and luminosity, showing signs of a very high rate of mass loss.-Characteristics:...
s, such as Rho Cassiopeiae
Rho Cassiopeiae
Rho Cassiopeiae is a yellow hypergiant star in the constellation Cassiopeia. It is about away from Earth, yet can still be seen by the naked eye , as it is 550,000 times as luminous as the Sun. On average, it has an absolute magnitude of −7.5, making it one of the most luminous stars known...
in the constellation Cassiopeia
Cassiopeia (constellation)
Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivalled beauty. Cassiopea was one of the 48 constellations listed by the 2nd century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today...
, 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
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
for a few million years before destroying themselves in a massive supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
or hypernova
Hypernova
Hypernova , also known as a type 1c Supernova, refers to an incredibly large star that collapses at the end of its lifespan...
. Yellow hypergiants are post-red supergiants, rapidly evolving toward the blue supergiant
Blue supergiant
Blue supergiants are supergiant stars of spectral type O or B.They are extremely hot and bright, with surface temperatures of 30,000-50,000 K. They typically have 10 to 50 solar masses on the Hertzsprung-Russell diagram, and can have radii up to about 25 solar radii...
phase. They are in a so-called "Yellow Evolutionary Void," a part of the Hertzsprung-Russell diagram where post-red supergiants exhibit atmospheric instability while evolving blueward; however, there exists strong chemical and surface gravity evidence that the brightest of the yellow supergiants, HD 33579, has not yet been to the red region. They can quickly run out of core nuclear fuel and implode to become Type II supernovae.
Internal structure
According to the current physical models of stars, a yellow hypergiant should possess a convectiveConvection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
core surrounded by a radiative
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
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
Degenerate matter
Degenerate matter is matter that has such extraordinarily high density that the dominant contribution to its pressure is attributable to the Pauli exclusion principle. The pressure maintained by a body of degenerate matter is called the degeneracy pressure, and arises because the Pauli principle...
.
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 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
- Rho CassiopeiaeRho CassiopeiaeRho Cassiopeiae is a yellow hypergiant star in the constellation Cassiopeia. It is about away from Earth, yet can still be seen by the naked eye , as it is 550,000 times as luminous as the Sun. On average, it has an absolute magnitude of −7.5, making it one of the most luminous stars known...
- V382 CarinaeV382 CarinaeV382 Carinae, also known as x Carinae , is a star in the constellation Carina.V382 Carinae is a yellow G-type hypergiant with a mean apparent magnitude of +3.93. It is 5930.90 light years from Earth. It is classified as a Cepheid variable star and its brightness varies from magnitude +3.84 to...
- V509 CassiopeiaeV509 CassiopeiaeV509 Cassiopeiae is a star in the constellation Cassiopeia.V509 Cassiopeiae is a yellow-white G-type hypergiant with a mean apparent magnitude of +5.10. It is at least 7800 light years from Earth. It is classified as a semiregular variable star and its brightness varies from magnitude +4.75 to...
(= HR 8752) - IRC+10420
- HD 33579
- IRAS 17163-3907IRAS 17163-3907IRAS 17163-3907 is a yellow hypergiant star located 13,000 light years from Earth in the constellation of Scorpius, making it the closest-known yellow hypergiant to Earth. The star is embedded in thick shells of expelled gases and dust, and owing to its appearance has been nicknamed by astronomers...
, aka The Fried Egg Nebula