Iota Orionis information

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
ι Orionis A
Spectral type	O9 III + B0.8 III/IV + B2:IV:
U−B color index	–1.08
B−V color index	–0.24
ι Orionis B
Spectral type	B8 III
Variable type	Orion
Astrometry
ι Orionis A
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	412+14; −13 pc
Orbit
Primary	ι Orionis Aa1
Companion	ι 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
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 Aa2
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
Mass	5.12 M☉
Surface gravity (log g)	4.0 cgs
Temperature	18,000 K
Age	~3 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
SIMBAD	ι 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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Observation data Epoch J2000 Equinox J2000
Location of ι Ori (circled)
Constellation	Orion
Right ascension	05^h 35^m 25.98191^s^[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 (R_v)	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]
Distance	412+14 −13^[4] pc

Orbit^[3]^[8]
Primary	ι Orionis Aa1
Companion	ι 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
Mass	23.1^[8] `M`_☉
Radius	8.3^[8] `R`_☉
Luminosity	68,000^[8] `L`_☉
Surface gravity (log g)	3.73^[3] cgs
Temperature	32,500^[3] K
Metallicity [Fe/H]	+0.10^[9] dex
Rotational velocity (v sin i)	122^[10] km/s
Age	4.0–5.5^[3] Myr
ι Ori Aa2
Mass	13.1^[8] `M`_☉
Radius	5.4^[8] `R`_☉
Luminosity	8,630^[8] `L`_☉
Surface gravity (log g)	3.78^[3] cgs
Temperature	27,000^[3] K
Age	9.4 ± 1.5^[3] Myr

ι Ori B
Mass	5.12^[11] `M`_☉
Surface gravity (log g)	4.0^[9] cgs
Temperature	18,000^[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
SIMBAD	ι Ori
	ι Ori B
	ι Ori C

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