Orange dwarf
Encyclopedia
A K-type main-sequence star (K V), also referred to orange dwarf, are main-sequence
(hydrogen
-burning) star
s of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence star
s and yellow G-type main-sequence stars. They have masses of from 0.5 to 0.8 times the mass
of the Sun
and surface temperature
s between 3,900 and 5,200 K
., Tables VII, VIII. Examples include Alpha Centauri B and Epsilon Indi
.
These stars are of particular interest in the search for extraterrestrial life
because they are stable on the main sequence for a very long time (15 to 30 billion years, compared to 10 billion for the Sun
). This may create an opportunity for life to evolve on terrestrial planets orbiting such stars. Orange dwarfs are about three to four times as abundant as sun-like stars, making planet searches easier.
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...
(hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
-burning) star
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...
s of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence star
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....
s and yellow G-type main-sequence stars. They have masses of from 0.5 to 0.8 times the mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
and surface temperature
Effective temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation...
s between 3,900 and 5,200 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
., Tables VII, VIII. Examples include Alpha Centauri B and Epsilon Indi
Epsilon Indi
Epsilon Indi is a K-type main-sequence star approximately 12 light-years away in the constellation of Indus. Two brown dwarfs, found in 2003, orbit the star.- Observation :...
.
These stars are of particular interest in the search for extraterrestrial life
Extraterrestrial life
Extraterrestrial life is defined as life that does not originate from Earth...
because they are stable on the main sequence for a very long time (15 to 30 billion years, compared to 10 billion for the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
). This may create an opportunity for life to evolve on terrestrial planets orbiting such stars. Orange dwarfs are about three to four times as abundant as sun-like stars, making planet searches easier.
See also
- Solar twins
- Red dwarfRed dwarfAccording 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....
- Stellar classification, Class K
- Star countStar countStar Counts are bookkeeping surveys of stars and the statistical and geometrical methods used to correct the survey data for bias. The surveys are most often made of nearby stars in the Milky Way Galaxy....
, survey of stars