Epsilon Canis Majoris is a binary star system and the second-brightest object in the constellation of Canis Major. Its name is a Bayer designation that is Latinised from ε Canis Majoris, and abbreviated Epsilon CMa or ε CMa. This is the 22nd-brightest star in the night sky with an apparent magnitude of 1.50. About 4.7 million years ago, it was the brightest star in the night sky, with an apparent magnitude of −3.99. Based upon parallax measurements obtained during the Hipparcos mission, it is about 430 light-years distant from the Sun. The two components are designated ε Canis Majoris A, officially named Adhara – the traditional name of the system, and B. Nomenclature ε Canis Majoris (Latinised to Epsilon Canis Majoris) is the binary system's Bayer designation. The designations of the two components as ε Canis Majoris A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). ε Canis Majoris bore the traditional name Adhara (sometimes spelled Adara, Adard, Udara or Udra), derived from the Arabic word عذارى 'aðāra', "virgins". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire star systems. It approved the name Adhara for the star ε Canis Majoris A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names. In the 17th-century catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Aoul al Adzari (أول العذاري awwal al-adhara), which was translated into Latin as Prima Virginum, meaning First of the Virgins. Along with δ Canis Majoris (Wezen), η Canis Majoris (Aludra) and ο2 Canis Majoris (Thanih al Adzari), these stars were Al ʽAdhārā (العذاري), 'the Virgins'. In Chinese, (), meaning Bow and Arrow, refers to an asterism consisting of ε Canis Majoris, δ Canis Majoris, η Canis Majoris, κ Canis Majoris, ο Puppis, π Puppis, χ Puppis, c Puppis and k Puppis. Consequently, ε Canis Majoris itself is known as (, ). Physical properties ε Canis Majoris is a binary star. The primary, ε Canis Majoris A, has an apparent magnitude of +1.5 and belongs to the spectral classification B2. Its color is blue or blueish-white, due to the surface temperature