Editing Alnitak (section)

{{short description|Triple star system in the constellation Orion}}
{{Starbox begin}}
{{Starbox image
| image=[[Image:Star-Alnitak.png|300px]]
| caption=Alnitak between the [[Horsehead Nebula]] and the [[Flame Nebula]]
}}
{{Starbox observe
| epoch=J2000
| ra={{RA|05|40|45.52666}}<ref name=hipparcos>{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|date=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}</ref>
| dec={{DEC|−01|56|34.2649}}<ref name=hipparcos/>
| appmag_v=1.77<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|date=2002}}</ref> {{nowrap|(2.08 + 4.28 + 4.01<ref name=hummel/>)}}
| constell=[[Orion (constellation)|Orion]]
| pronounce={{IPAc-en|æ|l|'|n|ai|t|æ|k}},<ref name=Kunitzsch>{{cite book
 |last1=Kunitzsch |first1=Paul
 |last2=Smart |first2=Tim
 |date = 2006 |edition = 2nd rev.
 |title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
 |publisher = Sky Pub |location = Cambridge, Massachusetts
 |isbn = 978-1-931559-44-7
}}</ref>
}}
{{Starbox character
| class=O9.5Iab + B1IV + B0III<ref name=hummel>{{Cite journal | doi = 10.1051/0004-6361/201321434| title = Dynamical mass of the O-type supergiant in ζ Orionis A| journal = Astronomy & Astrophysics| volume = 554| pages = A52| date = 2013| last1 = Hummel | first1 = C. A.| last2 = Rivinius | first2 = T. | last3 = Nieva | first3 = M. -F. | last4 = Stahl | first4 = O.| last5 = Van Belle | first5 = G.| last6 = Zavala | first6 = R. T.|arxiv = 1306.0330 |bibcode = 2013A&A...554A..52H | s2cid = 53645495}}</ref>
| b-v=−0.11 (A)<br />−0.20 (B)<ref name=tycho>{{cite journal|last1=Fabricius|first1=C.|last2=Høg|first2=E.|last3=Makarov|first3=V. V.|last4=Mason|first4=B. D.|last5=Wycoff|first5=G. L.|last6=Urban|first6=S. E.|title=The Tycho double star catalogue|journal=Astronomy and Astrophysics|volume=384|issue=1|date=2002|pages=180–189|issn=0004-6361|doi=10.1051/0004-6361:20011822|bibcode = 2002A&A...384..180F |doi-access=free}}</ref> |
| u-b=−1.06<ref name=ducati/>
| variable=
|type=[[Blue supergiant]] (Aa)}}
{{Starbox astrometry
| radial_v=18.50<ref name="KharchenkoScholz2007">{{cite journal|last1=Kharchenko|first1=N.V.|last2=Scholz|first2=R.-D.|last3=Piskunov|first3=A.E.|last4=Röser|first4=S.|last5=Schilbach|first5=E.|title=Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations|journal=Astronomische Nachrichten|volume=328|issue=9|date=2007|pages=889–896|issn=0004-6337|doi=10.1002/asna.200710776|arxiv = 0705.0878 |bibcode = 2007AN....328..889K |s2cid=119323941}}</ref>
| prop_mo_ra=3.19<ref name=hipparcos/>
| prop_mo_dec=2.03<ref name=hipparcos/>
| parallax=4.43
| p_error=0.64
| parallax_footnote=<ref name=hipparcos/>
| dist_ly={{cvt|387|±|54|pc|ly|disp=number}}
| dist_pc=387 ± 54<ref name=hummel/>
| absmag_v=−6.0 / −3.9 / −4.1<ref name=hummel/>
}}
{{Starbox orbit
| reference = <ref name=hummel/>
| primary = Aa
| name = Ab
| period_unitless = {{val|2,687.3|7.0|fmt=commas|u=d}}
| axis_unitless = {{val|35.9|0.2|ul=mas}}
| eccentricity = {{val|0.338|0.004}}
| inclination = {{val|139.3|0.6}}
| node = {{val|83.8|0.8}}
| periastron = JD {{val|2452734.2|9.0}}
| periarg = {{val|204.2|1.2}}
| k1 = 10.1
| k2 = 19.6
}}
{{Starbox orbit
| reference = <ref name=ORB6>{{cite web|url=https://crf.usno.navy.mil/wds-orb6|title=Sixth Catalog of Orbits of Visual Binary Stars|publisher=United States Naval Observatory}}</ref>
| primary=A
| name=B
| period=1,508.6
| axis=2.728
| eccentricity=0.07
| inclination=72.0
| node=155.5
| periarg=47.3
| periastron=2,070.6
}}
{{Starbox detail
 | component1=Alnitak Aa
 | mass={{val|33|10}}<ref name=hummel/>
 | radius={{val|20.0|3.2}}<ref name=hummel/>
 | luminosity=250,000<ref name=hummel/>
 | gravity = {{val|3.2|0.1}}<ref name=Raassen>{{cite journal|doi=10.1051/0004-6361:20077891|title=XMM-Newton observations of ζ Orionis (O9.7 Ib): A collisional ionization equilibrium model|journal=Astronomy and Astrophysics|volume=478|issue=2|pages=513|year=2008|last1=Raassen|first1=A. J. J.|last2=Van Der Hucht|first2=K. A.|last3=Miller|first3=N. A.|last4=Cassinelli|first4=J. P.|bibcode=2008A&A...478..513R|arxiv = 0803.0873 |s2cid=17601299}}</ref>
 | temperature = {{val|29,500|1,000|fmt=commas}}<ref name=hummel/>
 | rotational_velocity = {{val|110|10}}<ref name=hummel/>
 | rotation = 6.67 days<ref name=brite>{{cite journal|title=Understanding the photometric variability of ζ OriAa|author1=Buysschaert, B.|author2=Neiner, C.|author3=Ramiaramanantsoa, T.|author4=Richardson, N. D.|author5=David-Uraz, A.|author6=Moffat, A. F. J.|journal=Second Brite-Constellation Science Conference: Small Satellites – Big Science|arxiv=1610.05625|date=2016|volume=5|page=101|bibcode=2017sbcs.conf..101B}}</ref>
 | age_myr = 6.4<ref name=hummel/>
 | component2 = Alnitak Ab
 | mass2 = {{val|14|3}}<ref name=hummel/>
 | radius2 = {{val|7.3|1.0}}<ref name=hummel/>
 | luminosity2=32,000<ref name=hummel/>
 | temperature2 = 29,000<ref name=blazere>{{cite journal|bibcode=2015A&A...582A.110B|arxiv=1509.02773|title=The magnetic field of ζ Orionis A|journal=Astronomy & Astrophysics|volume=582|pages=A110|last1=Blazère|first1=A.|last2=Neiner|first2=C.|last3=Tkachenko|first3=A.|last4=Bouret|first4=J.-C.|last5=Rivinius|first5=Th.|year=2015|doi=10.1051/0004-6361/201526855|s2cid=62800990}}</ref>
 | gravirt = 4.0<ref name=blazere/>
 | age_myr2=7.2<ref name=hummel/>
}}
{{Starbox detail | no_heading=y
 | component1=Alnitak B
 | mass=
 | radius=
 | luminosity=
 | temperature=
 | rotational_velocity=350<ref name=hummel/>
 | age_myr=~7<ref name=hummel/>
}}
{{Starbox catalog
| names= {{odlist | B=ζ&nbsp;Orionis | F=50&nbsp;Orionis | name=[[Gould designation|126&nbsp;G.]]&nbsp;Orionis | BD=−02°1338 | SAO=132444 |HIP=26727 | TD1=5127 | WDS=J05407-0157 }}
| component1=A
| names1={{odlist | HR=1948 | HD=37742 }}
| component2=B
| names2={{odlist |HR=1949 | HD=37743 }}
}}
{{Starbox reference
| Simbad=Alnitak | sn=AB
| Simbad2=zet+Ori+A | sn2=A
| Simbad3=zet+Ori+B | sn3=B
}}
{{Starbox end}}

'''Alnitak''' is a triple [[star system]] in the [[constellation]] of [[Orion (constellation)|Orion]]. It has the designations '''ζ Orionis''', which is [[Latinisation of names|Latinised]] to '''Zeta Orionis''' and abbreviated '''Zeta Ori''' or '''ζ Ori''', and '''50 Orionis''', abbreviated '''50 Ori'''. The system is located at a distance of several hundred [[parsec]]s from the [[Sun]] and is one of the three main stars of [[Orion's Belt]] along with [[Alnilam]] and [[Mintaka]].

The primary [[star]], Alnitak Aa, is a hot [[blue supergiant]] with an absolute magnitude of −6.0 and is the brightest [[Stellar classification#Class O|class O]] star in the night sky with a visual magnitude of +2.0. It has two companions—Ab and B, the latter known for the longest time and the former discovered recently, producing a combined magnitude for the trio of +1.77. The stars are members of the [[Orion OB1 association]] and the {{ill|Collinder 70|de|vertical-align=sup}} association.