Alnitak

data from The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991)

note (category: star names):

ALNITAK; Alnitah.

position, motion, parallax:

position (J2000)	RA: 5h 40min 45.5sec	DEC: -1° 56' 34''
position (B1900)	RA: 5h 35min 42.7sec	DEC: -1° 59' 43''
proper motion (J2000)	RA: 0.003 arcsec/a	DEC: -0.002 arcsec/a
radial velocity	18 km/s note: spectroscopic binaries
rotational velocity	140 km/s (uncertain) (variable)
trigonometric parallax	0.024 arcsec
galactic coordinates	longitude: 206.45°	latitude: -16.59°

note (category: radial and/or rotational velocities):

Mass ejection up to 1800k/s.

note (category: dynamical parallaxes):

0.004".

magnitude

visual magnitude

2.05
(original HR magnitude)

spectral / color information

spectral class	O9.7Ib
B-V-magnitude	-0.21
U-B-magnitude	-1.07
R-I-magnitude
IR-note	object is infrared source (NASA merged infrared catalogue, Schmitz et al., 1978)

note (category: spectra):

Nitrogen deficient. Interstellar Lyman alpha absorption observed by AEROBEE rocket. Also classified O9.5Ib and O9.5Iab.

note (category: colors):

Color excess E(B-V) = +0.09.

variability information

variable star identification

2553

note (category: variability):

ADS 4263. Uncertain which component, HR 1948 or 1949, is the variable suspect.

double/multiple star system information

number of components of multiple star system	3
separation	2.4 arcsec
mag difference (of double or brightest multiple)	2.2
component ID	AB

note (category: double and multiple data):

AB 1.88 O9.5Ib, 4.02 B2III, 1508.6y, a = 2.728". Colors for combined light. Blended magnitude 1.76V, 18 and 6 solar masses. B is HR 1949. C is 9v at 58", possibly physical.

miscellaneous information

note (category: group membership):

Ori OB1b1; Orion belt; exciting star of HII region S277; HII region; IC 434.

note (category: stellar radii or diameters):

Diam. = 0.00047 - 0.00048".

note (category: miscellaneous):

In line of sight of high-velocity interstellar cloud.

data from SKY2000 - Master Star Catalog (Myers+ 1997)

position, motion, parallax:

position (J2000)	RA: 5h 40min 45.524sec	DEC: -1° 56' 33.53''	ą1.48 arcsec	source: 29
proper motion (J2000)	RA: 0.0002 arcsec/a	DEC: -0.002 arcsec/a		source: 25
radial velocity	18 km/s			source: 25
trigonometric parallax	0.024 arcsec		ą0.002 arcsec	source: 25
galactic coord. (B1950)	longitude: 206.46°	latitude: -16.59°

magnitude:

visual	2.03 (observed)	source: 25
photovisual	2.1	source: 2
photographic	1.8	source: 2

spectral information:

spectral class	B0		source: 96
Morgan-Keenan	O9.7Ib		source: 25
B-magnitude	1.82 ą0.05	B-V-magnitude	-0.21
U-magnitude	0.78 ą0.05	U-B-magnitude	-1.04

double/multiple star system information:

source of data: 19

separation between brightest and second brightest component	2.3 arcsec
magnitude difference between brightest and second brightest component	2.2
position angle	166 °

component	magnitude	spectral class	catalogue(s)/name(s)
A	2.03	B0	Alnitak, z Orionis, 50 Ori, HR 1948, HD 37742, SAO 132444
B	4.21	-	z Orionis, 50 Ori, HR 1949, HD 37743,

sources:

2	HD and HDE Catalogs
Cannon, A.J., and E.C. Pickering, Harvard Annals, Vols 91-99, 1918-24, Cambridge, Massachusetts: Harvard University; Cannon, A.J., Harvard Annals, Vol. 100, 1925-36, Cambridge, Massachusetts: Harvard University; and Cannon, A.J., and M. Walton Mayall, Harvard Annals, Vol. 112, 1949, Cambridge, Massachusetts: Harvard University
19	WDS Catalog
Worley, C.E., and G.G. Douglass, Washington Catalog of Visual Double Stars 1996.0, United States Naval Observatory, 1996
25	Bright Star Catalogue, 5th edition
Hoffleit, D. and Warren, W.H. Jr., The Bright Star Catalogue, 5th Revised Edition, Version 2, 1994
29	SAOJ2000
SAO on FK5 at J2000, 1989
96	SAO or HD/HDE Catalog
Reference from Value 1 or Reference from Value 2

data from Smithsonian Astrophysical Observatory Star Catalog (SAO Staff 1966; USNO, ADC 1990)

position and proper motion:

position (B1950)	RA: 5h 38min 14.043sec	DEC: -1° 58' 2.98''	ą0.006 arcsec
position (J2000)	RA: 5h 40min 45.524sec	DEC: -1° 56' 33.53''
proper motion B1950 (FK4)	RA: -0.0001 arcsec/a	DEC: -0.002 arcsec/a	ą0.001 arcsec/a in RA ą0.001 arcsec/a in DEC
proper motion J2000 (FK5)	RA: 0.0002 arcsec/a	DEC: -0.002 arcsec/a
source of proper motion data	Determined by source catalog

magnitude:

visual	2 (accuracy: 2 decimals)
source of visual magnitude data	Combined magnitude of component stars.

spectral information:

spectral class	B0
source of spectral data	Taken from the HD with M stars reclassified by Miss Cannon.

remarks for duplicity and variability

Double star - see source catalog for source

catalogues

source catalogue	FK3, catalogue number: 1631
Durchmusterung	BD-02 1338
Boss General Catalogue	7089
Henry Draper Catalogue	37742 The "SAO Catalog" entry refers to two consecutive HD numbers, the lower of which is given.

data from The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996)

position and proper motion:

position (J2000)	RA: 5h 40.7min	DEC: -1° 57'
proper motion (J2000)	RA: 0.001 arcsec/a	DEC: -0.005 arcsec/a

double/multiple star system information:

component	year	number of measures	position angle	angular separation	magnitude of 1st component	magnitude of 2nd component	spectral class(es)	discoverer code
AB	1822	often	151°	2.3''	2	4.2	O9.5Ibe	STF 774
AB	1990	often	166°	-	2	4.2	O9.5Ibe	STF 774
AC	1880	13	10°	57.6''	2	10	-	STF 774
BC	1909	1	8°	59.7''	4.2	8.5	B0	STF 774

discoverer information:

discoverer code	discoverer	reference
STF 774	Struve, F.G.W.	-

notes:

note	Zeta Ori. A premature orbit has been computed. Variable radial velocity of A not confirmed. C may be physical. Spectral types of AB: O9.5Ibe and B0III.

data from 4th Catalog of Orbits of Visual Binaries (Worley+, 1983)

position:

position (B1900)

RA: 5h 35.7min

DEC: -2° 0'

magnitudes, spectral classes, orbital elements:

author:	J. Hopmann
date of observation:	1955
magnitude of component A:	1.88
magnitude of component B:	1.88
spectral class component B:	O9.5I
spectral class component B:	O9.5I
period [y]:	1508.6
semi-major axis [arcsec]:	2.728
inclination [deg]:	72
node [deg]:	155.5
equinox of node:	1900
eccentricity:	0.07
time of periastron passage:	2070.6
dates of ephemeris:	1950-2000
grade:	indeterminate
reference:	Mitt. Sternw. Wien 13, 49; 1967.

notes

Suspected RV variation of star A not confirmed. Star C (mag. about 9, 60") may be physical.

other name(s)

STF 774, Zeta Ori

data from Combined General Catalogue of Variable Stars (suspected variables) (Kholopov+ 1998)

position:

position (equinox 1950.0)

RA: 5h 38min 14sec

DEC: -1° 58' 3''

variability informations:

magnitute at max. brightness	1.72
magnitute at min. brightness	1.79
photometric system	visual, photovisual or Johnson's V

spectral information

spectral class

references

to a study

480402D (designation: zeta ORI)

miscanellous

There are notes in the published catalog (Kukarkin et al.(1982)).

catalogues and names	Alnitak, z Ori, NSV 02553, 50 Ori, HR 1948, HD 37742, SAO 132444, BD -2 1338, WDS 05407-0157A
other names	Alnitah
constellation	Orion