Blue dwarf (red dwarf stage)
Encyclopedia
A blue dwarf is a hypothetical class of star
that develops from a red dwarf
star after it has exhausted much of its hydrogen fuel supply. Since red dwarf stars fuse
their hydrogen slowly and are fully convective
(allowing a larger percentage of their total hydrogen supply to be fused), the universe is currently not old enough for any blue dwarfs to have formed yet. Their existence is predicted based on theoretical models.
Stars increase in luminosity
as they age, and a more luminous star needs to radiate energy more quickly to maintain equilibrium. Stars larger than red dwarfs do this by increasing their size and becoming red giant
s with larger surface areas. Rather than expanding, however, red dwarfs are predicted to increase their radiative rate by increasing their surface temperature
s and becoming "bluer". This is because the surface layers of red dwarfs do not become significantly more opaque with increasing temperature.
Blue dwarfs eventually evolve into white dwarf
s once their hydrogen fuel is completely exhausted.
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...
that develops from a red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
star after it has exhausted much of its hydrogen fuel supply. Since red dwarf stars fuse
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
their hydrogen slowly and are fully convective
Convection
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....
(allowing a larger percentage of their total hydrogen supply to be fused), the universe is currently not old enough for any blue dwarfs to have formed yet. Their existence is predicted based on theoretical models.
Stars increase in luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
as they age, and a more luminous star needs to radiate energy more quickly to maintain equilibrium. Stars larger than red dwarfs do this by increasing their size and becoming red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...
s with larger surface areas. Rather than expanding, however, red dwarfs are predicted to increase their radiative rate by increasing their surface temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
s and becoming "bluer". This is because the surface layers of red dwarfs do not become significantly more opaque with increasing temperature.
Blue dwarfs eventually evolve into white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
s once their hydrogen fuel is completely exhausted.