Nu Draconis (also known as ν Dra, ν Draconis, where ν is the Greek letter nu, or traditionally as Kuma ) is a double star in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Draco. The respective components are designated ν¹ Draconis and ν² Draconis. The second component is a spectroscopic binary star system. This star, along with β Dra (Rastaban), γ Dra (Eltanin), μ Dra (Alrakis) and ξ Dra (Grumium) were Al ʽAwāïd, "the Mother Camels", which was later known as the Quinque Dromedarii. In Chinese, (), meaning '' Celestial Flail'', refers to an asterism consisting of ν Draconis, ξ Draconis, β Draconis, γ Draconis and ι Herculis. Consequently, the Chinese name for ν Draconis itself is (, .)香港太空館 - 研究資源 - 亮星中英對照表
, Hong Kong Space Museum. Accessed on line November 23, 2010. The two stars of the visual binary are considered to be a common proper motion pair on the basis of their very similar

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

es, radial velocities, and

proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

s, although no orbital motion can be observed. ν¹ Draconis is an Am star, a slowly rotating chemically peculiar star with abnormally strong metallic absorption lines in its spectrum. Its spectral type of kA3hF0mF0 means that it would have a spectral class of A3 if determined solely from its calcium K lines, F0 if determined from its

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

lines, and F0 if determined from other metallic spectral lines. ν² Draconis is a spectroscopic binary with a period of 38 days. The two stars are separated by 0.267 au on average, and they have an almost circular orbit with an eccentricity of 0.03. The primary is also an Am star, while the secondary has a low mass and luminosity and is only inferred from the orbital movement of the more massive star.

References

External links

* Kaler, James
Kuma
{{Authority control Triple star systems Draco (constellation) Draconis, Nu Draconis, 24 5 A-type main-sequence stars 085819 29 159541 60 Durchmusterung objects 6554 5 Am stars A-type subgiants