Xi1 Ceti

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Xi1 Ceti A
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension 02h 12m 59.995s[1]
Declination +08° 50′ 48.16″[1]
Apparent magnitude (V) +4.37 [combined]
Spectral type G, 6 or 8, III[2]
Proper motion (μ) RA: –26.87 ± 0.48[1] mas/yr
Dec.: –17.23 ± 0.36[1] mas/yr
Parallax (π) 8.51 ± 0.51[1] mas
Distance 380 ± 20 ly
(118 ± 7 pc)
Absolute magnitude (MV) –0.866[2]
Mass 4[2] M
Radius 1.7[2] R
Luminosity 190[2] L
Temperature 4200[2] K
Age 300[2] Myr
Other designations
65 Ceti, HR 649, HD 13611, HIP 10324
Database references
Exoplanet Archive data

Xi1 Ceti1 Ceti), is a binary system located in the constellation Cetus, suspected as a ternary.

In Chinese, 天囷 (Tiān Qūn), 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, Xi1 Ceti itself is known as the Fifth Star of Circular Celestial Granary, Tiān Qūn Wu.[3]

The spectroscopic binary nature of Xi1 Ceti was discovered in 1901 by William Wallace Campbell using the Mills spectrograph at the Lick Observatory.[4][5] 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.