An Etymological Dictionary of Astronomy and Astrophysics

The sixth brightest star in the sky, Capella lies in the Northern Hemisphere → constellation  → Auriga. Also known as HD 34029 = HR 1708 = HIP 24608.

Capella lies about 42 → light-years away (13.159 ± 0.015 → parsecs).

Its → apparent visual magnitude is V = 0.07. A → spectroscopic binary, it consists of a pair of G8 III and G0 III → giants with an → orbital period of 104 days.

The more evolved former/→ primary star has a slightly larger mass and luminosity (2.6 Msun and 79 Lsun) than that of the latter/→ secondary star (2.5 Msun and 73 Lsun). The primary is a typical late G giant presumably in the He-burning stage (→ red clump), which is lithium deficient and a slow rotator as other normal giants. In contrast, the secondary is a fast rotator (projected rotational velocity is v_e sin i ~ 35 km s-1) with high stellar activity (characterized by conspicuous chromospheric emission lines in UV) and shows a remarkably strong Li line, which indicates that the initial Li content is almost retained without being diluted (the surface Li composition for the secondary is ~100 times higher than that for the primary). That is, the secondary star belongs to the unusual group of Li-rich giants (see, e.g., Takeda et al., 2018, ApJ 862, 57 and Torres et al., 2015, ApJ 807, 26).

Etymology (EN): From L. capella “little she-goat,” diminutive of caper “goat.”

Etymology (PE): Bozbân “goat keeper” (Biruni, A.D. 973-1048, in his Tafhim), from boz, → goat, + -bân prefix denoting “keeper.”
Ayyuq, loan from Ar.