Iota Orionis

ι Orionis
Location of ι Ori (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 35m 25.98191s[1]
Declination –05° 54′ 35.6435″[1]
Apparent magnitude (V) 2.77[2]
Characteristics
ι Orionis A
Spectral type O9 III + B0.8 III/IV[3] + B2:IV:[4]
U−B color index –1.08[2]
B−V color index –0.24[2]
ι Orionis B
Spectral type B8 III[5]
Variable type Orion[6]
Astrometry
ι Orionis A
Radial velocity (Rv)21.5[7] km/s
Proper motion (μ) RA: +1.42[1] mas/yr
Dec.: –0.46[1] mas/yr
Parallax (π)1.40 ± 0.22 mas[1]
Distance412+14
−13[4] pc
Orbit[3][8]
Primaryι Orionis Aa1
Companionι Orionis Aa2
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 Aa1
Mass23.1[8] M☉
Radius8.3[8] R☉
Luminosity68,000[8] L☉
Surface gravity (log g)3.73[3] cgs
Temperature32,500[3] K
Metallicity [Fe/H]+0.10[9] dex
Rotational velocity (v sin i)122[10] km/s
Age4.0–5.5[3] Myr
ι Ori Aa2
Mass13.1[8] M☉
Radius5.4[8] R☉
Luminosity8,630[8] L☉
Surface gravity (log g)3.78[3] cgs
Temperature27,000[3] K
Age9.4 ± 1.5[3] Myr
ι Ori B
Mass5.12[11] M☉
Surface gravity (log g)4.0[9] cgs
Temperature18,000[9] K
Age~3[9] Myr
Other designations
Hatysa, ι Orionis, Na'ir al Saif, Hatsya, BD−06°1241, FK5 209, SAO 132323, ADS 4193, WDS J05354-0555
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
SIMBADι Ori
ι Ori B
ι Ori C

Iota Orionis (ι Orionis, abbreviated 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 1,340 light-years (412 parsecs) from the Sun.

The system has three visible components designated Iota Orionis A, B and C. Iota Orionis A has also been resolved using speckle interferometry and is also a massive spectroscopic binary, with components Iota Orionis Aa1 (officially named Hatysa /hɑːˈtiːsə/), Aa2, and Ab.

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