Zeta Arae is the third-brightest star in the southern constellation Ara. Its name is a Bayer designation that is Latinized from ζ Arae, and abbreviated Zeta Ara or ζ Ara. The apparent visual magnitude of this star is 3.1, which can be seen with the naked eye from suburban skies in the southern hemisphere. From the parallax measurements, it is located at a distance of approximately from Earth. The star is drifting closer to the Sun with a radial velocity of 6 km/s.
The spectrum of this star matches a stellar classification of K3 III. The luminosity class of 'III' indicates this is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence. However, some studies have suggested it is instead a supergiant. The star has 7-8 times the mass of the Sun and has expanded to 114 times the Sun's girth. It is radiating 3,800 times the luminosity of the Sun from its photosphere at an effective temperature of 4,246 K, giving it the orange hue of a K-type star.
In 1997, an excess of infrared emission was announced that may indicate circumstellar matter. However, a 2015 study found no excess. A candidate gravitationally bound companion was announced in 2022. This object lies at an angular separation of from Zeta Arae, which is equivalent to a projected separation of .
Nomenclature In Chinese, (), meaning Tortoise, refers to an asterism consisting of ζ Arae, ε1 Arae, γ Arae, δ Arae and η Arae. 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, . Consequently, the Chinese name for ζ Arae itself is (, .) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 1 日
R. H. Allen called it Tseen Yin , together with δ Arae, from the Chinese 天陰 (Mandarin pronunciation tiānyīn) "dark sky". However, 天陰 is in Aries.Chevalier, S., and Tsuchihashi, P., (1911): "Catalogue d'Étoiles fixes, observés a Pekin sous l'Empereur Kien Long (Qianlong (Chien-Lung)), XVIIIe siecle", Annales de l'Observatoire Astronomique de Zô-Sé. (Yi Shi Tong) (1981): . so Allen probably confused constellation "Ara" with "Ari".
References
External links HR 6285 Image Zeta Arae