Hatsya identified in a Stellarium screenshot.
Epoch J2000 Equinox J2000
|Right ascension||05h 35m 25.98191s|
|Declination||–05° 54′ 35.6435″|
|Apparent magnitude (V)||2.77|
|Spectral type||O9 III + B0.8 III/IV|
|U−B color index||–1.08|
|B−V color index||–0.24|
|Radial velocity (Rv)||21.5 km/s|
|Proper motion (μ)||RA: +1.42 mas/yr
Dec.: –0.46 mas/yr
|Parallax (π)||1.40 ± 0.22 mas|
|Distance||approx. 2,300 ly
(approx. 700 pc)
|Period (P)||29.1338 days|
|Periastron epoch (T)||2,450,072.80 HJD|
|ι Ori A|
|Surface gravity (log g)||3.73 cgs|
|Metallicity [Fe/H]||+0.10 dex|
|Rotational velocity (v sin i)||122 km/s|
|ι Ori B|
|Surface gravity (log g)||3.78 cgs|
|Age||9.4 ± 1.5 Myr|
Iota Orionis (ι Ori, ι Orionis) is a star in the equatorial constellation of Orion the hunter. The apparent visual magnitude of Iota Orionis is 2.77, making it the eighth brightest member of Orion. It is the brightest star in an asterism known as Orion's sword. Iota Orionis has the traditional names Hatsya (sometimes with the typographic error Hatysa) and in Arabic, Na’ir al Saif, which means simply "the Bright One of the Sword." From parallax measurements, it is located at a distance of roughly 2,330 light-years (710 parsecs) from Earth.
Iota Orionis is a quadruple system dominated by a massive spectroscopic binary with an eccentric (e=0.764), 29-day orbit. The binary is composed of a stellar class O9 III star (blue giant) and a class B0.8 III/IV star, with the secondary being about 2 magnitudes fainter. The collision of the stellar winds from this pair makes the system a strong X-ray source. Oddly, the two objects of this system appear to have different ages, with the secondary being about double the age of the primary. In combination with the high eccentricity of their orbit, this suggests that the binary system was created through a capture, rather than by being formed together and undergoing a mass transfer. This capture may have occurred, for example, through an encounter between two binary systems.
- van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Astronomy and Astrophysics Supplement Series 34: 1–49. Bibcode:1978A&AS...34....1N.
- Bagnuolo et al. (June 2001), "ι Orionis-Evidence for a Capture Origin Binary", The Astrophysical Journal 554 (1): 362–367, Bibcode:2001ApJ...554..362B, doi:10.1086/321367
- Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, retrieved 2009-09-10
- Conti, P. S.; Loonen, J. P. (October 1970), "Coarse analysis of the helium weak B star Iota Ori B", Astronomy and Astrophysics 8: 197–203, Bibcode:1970A&A.....8..197C
- Uesugi, Akira; Fukuda, Ichiro (1970), "Catalogue of rotational velocities of the stars", Contributions from the Institute of Astrophysics and Kwasan Observatory (University of Kyoto), Bibcode:1970crvs.book.....U
- Bakich, Michael E. (1995), The Cambridge Guide to the Constellations, Cambridge University Press, p. 118, ISBN 0521449219
- Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 317