Ι Orionis
 Location of ι Ori (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Orion |
| Right ascension | 05h 35m 25.98191s |
| Declination | –05° 54′ 35.6435″ |
| Apparent magnitude (V) | 2.77 |
| Characteristics | |
| Spectral type | O9 III + B0.8 III/IV |
| U−B color index | –1.08 |
| B−V color index | –0.24 |
| Variable type | (B) Orion |
| Astrometry | |
| Radial velocity (Rv) | 21.5 km/s |
| Proper motion (μ) |
RA: +1.42 mas/yr Dec.: –0.46 mas/yr |
| Parallax (π) | 1.40 ± 0.22mas |
| Distance | approx. 2,300 ly (approx. 700 pc) |
| Orbit | |
| Period (P) | 29.1338 days |
| Semi-major axis (a) | 132 R☉ |
| Eccentricity (e) | 0.764 |
| Inclination (i) | ~60° |
| Periastron epoch (T) | 2,450,072.80 HJD |
| Details | |
| ι Ori Aa | |
| Mass | 23.1 M☉ |
| Radius | 8.3 R☉ |
| Luminosity | 68,000 L☉ |
| Surface gravity (log g) | 3.73 cgs |
| Temperature | 32,500 K |
| Metallicity [Fe/H] | +0.10 dex |
| Rotational velocity (v sin i) | 122 km/s |
| Age | 4.0–5.5 Myr |
| ι Ori Ab | |
| Mass | 13.1 M☉ |
| Radius | 5.4 R☉ |
| Luminosity | 8,630 L☉ |
| Surface gravity (log g) | 3.78 cgs |
| Temperature | 27,000 K |
| Age | 9.4 ± 1.5 Myr |
| ι Ori B | |
| Surface gravity (log g) | 4.0 cgs |
| Temperature | 18,000 K |
| Age | ~3 Myr |
| Other designations | |
| ι Ori A: 44 Orionis, HD 37043, HIP 26241, HR 1899, 2MASS J05352597-0554357 | |
| ι Ori B: V2451 Ori, 2MASS J05352645-0554445 | |
| ι Ori C: 2MASS J05352920-0554471 | |
| Database references | |
| SIMBAD | ι Ori |
| ι Ori B | |
| ι Ori C | |
Iota Orionis (ι Orionis, abbreviated Iot Ori, ι Ori) is a multiple star system in the equatorial constellation of Orion the hunter. It is the eighth-brightest member of Orion with an apparent visual magnitude of 2.77 and also the brightest member of the asterism known as Orion's Sword. It is a member of the NGC 1980 open cluster. From parallax measurements, it is located at a distance of roughly 1,330 light-years (410 parsecs) from the Sun.
The system has three components designated Iota Orionis A, B and C. Iota Orionis A is itself a massive spectroscopic binary, with components Iota Orionis Aa (also named Hatysa) and Ab.
ι Orionis (Latinised to Iota Orionis) is the system's Bayer designation. The designations of the three constituents as Iota Orionis A, B and C, and those of A's components - Iota Orionis Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
The system bore the traditional names Hatysa or Hatsya In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Hatysa for the component Iota Orionis Aa on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.
In Arabic the system was known as Na’ir al Saif, which means "the Bright One of the Sword."
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