Upsilon Draconis (υ Dra) is a
binary star[ system in the northern ]circumpolar constellation
A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest po ...
of Draco
Draco is the Latin word for serpent or dragon.
Draco or Drako may also refer to:
People
* Draco (lawgiver) (from Greek: Δράκων; 7th century BC), the first lawgiver of ancient Athens, Greece, from whom the term ''draconian'' is derived
* ...
. It is faintly visible to the naked eye with an apparent visual magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...
of 4.83.[ Based upon an annual parallax shift of 9.48 mas as measured from Earth, it is located around 340 light years from the ]Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.02 due to interstellar dust
Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...
.[
In ]Chinese
Chinese can refer to:
* Something related to China
* Chinese people, people of Chinese nationality, citizenship, and/or ethnicity
**''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation
** List of ethnic groups in China, people of ...
, (), meaning '' Left Wall of Purple Forbidden Enclosure'', refers to an asterism consisting of υ Draconis, ι Draconis, η Draconis, ζ Draconis, θ Draconis, 73 Draconis 73 may refer to:
* 73 (number)
* one of the years 73 BC, AD 73, 1973, 2073
* ''73'' (magazine), a United States-based amateur radio magazine
* 73 Best regards, a popular Morse code abbreviation
* '' No. 73'', a British 1980s children's TV show
*N ...
, γ Cephei and 23 Cassiopeiae.[ ''中國星座神話'', written by 陳久金. Published by 台灣書房出版有限公司, 2005, .]
This is a single-lined spectroscopic binary star system with an orbital period
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...
of 258.48 days and an eccentricity
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-Centre (geometry), center, in geometry
* Eccentricity (g ...
of 0.21.[ The primary, component A, is an ]evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
K-type giant star
A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...
with a stellar classification of K0 III.[ It is a suspected ]barium star
Barium stars are spectral class G to K stars whose spectra indicate an overabundance of s-process elements by the presence of singly ionized barium, Ba II, at λ 455.4 nm. Barium stars also show enhanced spectral features of carbon, the ...
, which may indicate the orbiting companion, component B, is a white dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...
star.[
The measured ]angular diameter
The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it is ...
of the primary, after correction for limb darkening
Limb darkening is an optical effect seen in stars (including the Sun), where the central part of the disk appears brighter than the edge, or ''limb''. Its understanding offered early solar astronomers an opportunity to construct models with such ...
, is .[ At the estimated distance of Upsilon Draconis, this yields a physical size of about 19 times the Sun's radius.][ It is about 1.37][ billion years old with an estimated 2.05][ times the mass of the Sun. The star is radiating 2.23][ times the ]solar luminosity
The solar luminosity (), is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun.
One nominal ...
from its photosphere at an effective temperature of 4,561 K.[
]
References
{{Stars of Draco, state=collapsed
K-type giants
Barium stars
Draco (constellation)
Draconis, Upsilon
Durchmusterung objects
Draconis, 52
176524
092782
7180
Spectroscopic binaries