Zeta Draconis
A binary giant star, fifth-brightest in Draco, with a traditional Arabic name.
Zeta Draconis, also known by its Bayer designation ζ Draconis, is a binary star system located in the northern circumpolar constellation Draco. It shines at an apparent visual magnitude of +3.17, making it the fifth-brightest star in this generally dim constellation. Parallax measurements place it roughly 330 light-years from the Sun.
The system consists of two components: Zeta Draconis A, which carries the formal name Aldhibah, and Zeta Draconis B. The "A" and "B" designations follow the convention of the Washington Multiplicity Catalog, later adopted by the International Astronomical Union.
The name Aldhibah comes from the old Arabic word الذئب (al-dhiʼb), meaning "the wolf" or "the hyena." In its feminine form, Al Dhiʼbah, it was recorded by R.H. Allen in 1899, though he mistranslated it as the plural "hyenas." The star shares a dual form of the name, الذئبين (al-dhiʼbayn), with Eta Draconis. It is also known historically as Nodus III, or "Third Knot," referring to a loop in the tail of Draco. In 2016, the IAU’s Working Group on Star Names approved Aldhibah specifically for Zeta Draconis A on 5 September 2017.
In Chinese astronomy, Zeta Draconis is part of an asterism called the Left Wall of Purple Forbidden Enclosure, which also includes Iota Draconis, Eta Draconis, Theta Draconis, Upsilon Draconis, 73 Draconis, Gamma Cephei, and 23 Cassiopeiae. Within this asterism, Zeta Draconis itself is known as 上弼 (Shǎngbì), meaning "the First Minister" or, as R.H. Allen westernized it, "the Higher Minister."
Zeta Draconis A is a giant star with a stellar classification of B6 III. It is roughly six times larger and more massive than the Sun, and it radiates about 880 times the Sun’s luminosity. Its outer envelope has an effective temperature of nearly 13,400 K, and its equatorial rotation velocity is at least 55 km/s.
The north ecliptic pole lies at right ascension 18h and declination +66.5°, roughly midway between Delta Draconis and Zeta Draconis. This pole nearly coincides with the south celestial pole of Venus, and Zeta Draconis also serves as the north pole star of Jupiter.
Quick Facts
- Apparent visual magnitude
- +3.17
- Distance from sun
- roughly 330 ly
Facts from the source article.
Lore & Background
The system's Bayer designation is Zeta Draconis. Its two components are designated Zeta Draconis A and B, following the convention of the Washington Multiplicity Catalog. The traditional name Aldhibah, approved by the IAU Working Group on Star Names in 2017 for component A, derives from the old Arabic name الذئب al-dhiʼb, meaning 'the wolf' or 'the hyena', given in its feminine form 'Al Dhiʼbah' in Allen (1899), though he mistranslated it as plural 'hyenas'. The system shares the dual form of the name, الذئبين al-dhiʼbayn, with Eta Draconis. It is also known as Nodus III (Third Knot), referring to a loop in the tail of Draco. In Chinese, the star is part of an asterism called Left Wall of Purple Forbidden Enclosure, and its own Chinese name is 上弼 (Shǎngbì), westernized as Shang Pih by R.H. Allen with the meaning 'the Higher Minister'.
Reader's Guide
Zeta Draconis holds significance as a bright marker in the faint constellation Draco, serving as the fifth-brightest star in that region. Its traditional name Aldhibah, along with the related name Athebyne for Eta Draconis, reflects a shared Arabic heritage that links the two stars as a pair. The star's alternative designation Nodus III places it within a historical framework of celestial mapping, where knots in Draco's tail were named. Astronomically, Zeta Draconis A is a giant star of spectral type B6 III, radiating 880 times the Sun's luminosity from an effective temperature near 13,400 K, with a rotation velocity of at least 55 km/s at the equator. The system's distance of roughly 330 light-years was determined via parallax. Notably, the north ecliptic pole lies roughly midway between Delta Draconis and Zeta Draconis, and Zeta Draconis is the north pole star of Jupiter. The IAU's formal approval of the name Aldhibah in 2017 for component A standardizes its nomenclature for modern use.
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