Xi1 Ceti
Xi1 Ceti , is a binary system located in the constellation Cetus, suspected as a ternary.
In Chinese, 天囷, meaning Circular Celestial Granary, refers to an asterism consisting of α Ceti, κ1 Ceti, λ Ceti, μ Ceti, ξ1 Ceti, ξ2 Ceti, ν Ceti, γ Ceti, δ Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for Xi1 Ceti itself is "the Fifth Star of Circular Celestial Granary", Tiān Qūn Wu.
The spectroscopic binary nature of Xi1 Ceti was discovered in 1901 by William Wallace Campbell using the Mills spectrograph at the Lick Observatory. The primary Ceti A is a G6III or G8III clump-giant star. The spectroscopic binary companion star is an A2V dwarf of about 2 solar masses and 30 luminosity. It is separated at 0.012 arcsec so in an orbit of 4.2 AU, smaller than the distance between Jupiter and the Sun.
Xi1 Ceti A exhibits characteristics similar to an eclipsing binary, with a small white dwarf companion. Occultations with the moon have not yet confirmed the existence of the second suspected companion. However, component A is a barium star which would tend to confirm this unseen component.
