Nu Draconis

𝜈 Draconis

𝜈 Draconis in optical light
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
𝜈1 Dra
Right ascension 17h 32m 10.56856s[1]
Declination +55° 11′ 03.2739″[1]
Apparent magnitude (V) +4.88[2]
𝜈2 Dra
Right ascension 17h 32m 16.02464s[1]
Declination +55° 10′ 22.6504″[1]
Apparent magnitude (V) +4.88[2]
Characteristics
𝜈1 Dra
Spectral type A8Vm[3] (kA3hF0mF0[4])
U−B color index +0.03[2]
B−V color index +0.26[2]
𝜈2 Dra
Spectral type A4IVm[3] (kA3hF1mF0[4])
U−B color index +0.04[2]
B−V color index +0.27[2]
Astrometry
𝜈1 Dra
Radial velocity (Rv)–15.2[5] km/s
Proper motion (μ) RA: +147.39[1] mas/yr
Dec.: +54.31[1] mas/yr
Parallax (π)33.06 ± 0.15 mas[1]
Distance98.7 ± 0.4 ly
(30.2 ± 0.1 pc)
𝜈2 Dra
Radial velocity (Rv)–16.0[5] km/s
Proper motion (μ) RA: +142.65[1] mas/yr
Dec.: +62.43[1] mas/yr
Parallax (π)32.80 ± 0.18 mas[1]
Distance99.4 ± 0.5 ly
(30.5 ± 0.2 pc)
Orbit[6]
Primary𝜈2 Dra A
Companion𝜈2 Dra B
Period (P)38.034 days
Eccentricity (e)0.03
Semi-amplitude (K1)
(primary)		10.0 km/s
Details
𝜈1 Dra
Mass1.85[7] M☉
Surface gravity (log g)4.2[8] cgs
Temperature7,533[8] K
Metallicity+0.03[8]
Rotational velocity (v sin i)86[9] km/s
Age13.0[10] Myr
𝜈2 Dra
Mass1.61 + 0.24[7] M☉
Radius1.812[11] R☉
Surface gravity (log g)4.11[12] cgs
Temperature7,272[8] K
Rotational velocity (v sin i)68[9] km/s
Other designations
𝜈 Draconis, 𝜈 Dra, Kuma
𝜈1 Dra: 24 Dra, BD+55 1944, FK5 655, HD 159541, HIP 85819, HR 6554, SAO 30447[13]
𝜈2 Dra: 25 Dra, BD+55 1945, FK5 657, HD 159560, HIP 85829, HR 6555, SAO 30450[14]
Database references
SIMBAD𝜈 Dra
𝜈1 Dra
𝜈2 Dra

Nu Draconis (also known as 𝜈 Dra, 𝜈 Draconis, where 𝜈 is the Greek letter nu, or traditionally as Kuma /ˈkjuːmə/) is a double star in the constellation Draco. The respective components are designated 𝜈1 Draconis and 𝜈2 Draconis. The second component is a spectroscopic binary star system.[14]

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.[15]

In Chinese, 天棓 (Tiān Bàng), meaning Celestial Flail, refers to an asterism consisting of 𝜈 Draconis, ξ Draconis, β Draconis, γ Draconis and ι Herculis.[16] Consequently, the Chinese name for 𝜈 Draconis itself is 天棓二 (Tiān Bàng èr, English: the Second Star of Celestial Flail.)[17]

The two stars of the visual binary are considered to be a common proper motion pair on the basis of their very similar parallaxes, radial velocities, and proper motions, although no orbital motion can be observed.[18]

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 lines, and F0 if determined from other metallic spectral lines.[4]

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.[19][6] 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.[7]

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  16. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  17. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-29 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
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