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A K-type main-sequence star, also referred to as a K-type dwarf, or orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("red dwarfs") and yellow/white G-type main-sequence stars .
The modern designations of its entry in Ulugh Beg's catalogue are "U 781" and "Eri 13" (the latter is the same as Ptolemy's catalogue designation). [36] [37] In 1598 Epsilon Eridani was included in Tycho Brahe's star catalogue, republished in 1627 by Johannes Kepler as part of his Rudolphine Tables.
The common use of "dwarf" to mean the main sequence is confusing in another way because there are dwarf stars that are not main-sequence stars. For example, a white dwarf is the dead core left over after a star has shed its outer layers, and is much smaller than a main-sequence star, roughly the size of Earth. These represent the final ...
Sub-dwarf classes have also been used: VI for sub-dwarfs (stars slightly less luminous than the main sequence). Nominal luminosity class VII (and sometimes higher numerals) is now rarely used for white dwarf or "hot sub-dwarf" classes, since the temperature-letters of the main sequence and giant stars no longer apply to white dwarfs.
K-type main-sequence stars, also known as orange dwarfs, may be candidates for supporting extraterrestrial life.These stars are known as "Goldilocks stars" as they emit enough radiation in the non-UV ray spectrum [1] to provide a temperature that allows liquid water to exist on the surface of a planet; they also remain stable in the main sequence longer than the Sun by burning their hydrogen ...
HD 189733 A is an orange dwarf star of the spectral type K1.5V. The star has a mass of 81 percent that of the Sun, a radius of 76 percent, and a luminosity of 33 percent. The star is between 89 and 102 percent as enriched in iron as the Sun, making the star more than 600 million years old. Its absolute magnitude is 6.2.
39 Eridani is a binary star also divisible in small amateur telescopes, 206 light-years from Earth. The primary is an orange-hued giant star of magnitude 4.9 and the secondary is of magnitude 8. 40 Eridani is a triple star system consisting of an orange main-sequence star, a white dwarf, and a red dwarf. The orange main-sequence star is the ...
Epsilon Coronae Borealis, Latinized from ε Coronae Borealis, is a multiple star system in the constellation Corona Borealis located around 230 light-years from the Solar System. It shines with a combined apparent magnitude of 4.13, [9] meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations ...