Magnitude 4.63 Apparent magnitude (V) 4.63 | Constellation Orion | |
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Chi2 Orionis (Chi2 Ori / χ2 Orionis / χ2 Ori) is a B-type supergiant star in the constellation of Orion. It has an apparent visual magnitude of 4.63. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
Contents
Chi1 Orionis is an unrelated yellow main sequence star over two degrees away.
Spectrum
χ2 Orionis has a B2 bright supergiant spectrum and is one of the standard B2 Ia stars. It has been reported as having unusually narrow absorption lines and some weak emission lines and was included as one of the original Be stars. It is no longer treated as a Be star since many supergiants show some emission features at high resolution and Be stars is usually defined to exclude supergiants.
Variability
χ2 Orionis was listed as a likely small amplitude variable star based on photometry for the Third Catalogue of Stars measured in the Geneva Observatory Photometric System. The amplitude was measured as 22 thousandths of a magnitude. It was included in the General Catalogue of Variable Stars based on Hipparcos satellite photometry with a magnitude range (in the Hipparchos photometric system) of 4.68 - 4.72 and a period of 2.8 days. A detailed study of the Hipparcos photometry confirmed the star as an α Cyg variable and gave the amplitude of variation as 0.057 magnitudes.