Editing Deneb

{{short description|Star in the constellation Cygnus}}
{{About|the star}}
{{Starbox begin}}
{{Starbox image
 | image=
   {{Location mark
     | image=Cygnus constellation map.svg
     | float=center | width=250 | position=right
     | mark=Red circle.svg | mark_width=10 | mark_link=Deneb (star)
     | x%=32.5 | y%=36.9
   }}
 | caption=Location of Deneb
}}
{{Starbox observe
 | epoch=J2000
 | constell=[[Cygnus (constellation)|Cygnus]]
 | pronounce={{IPAc-en|'|d|ɛ|n|ɛ|b|}}, {{IPAc-en|'|d|ɛ|n|ə|b|}}<ref name=merriam>{{cite book|author=Merriam-Webster, Inc|title=Merriam-Webster's Collegiate Dictionary|url=https://books.google.com/books?id=53-PQgAACAAJ|year=1998|publisher=Merriam-Webster|isbn=978-0-87779-714-2}}</ref>
 | ra={{RA|20|41|25.9}}<ref name=hipparcos/>|dec={{DEC|+45|16|49}}<ref name=hipparcos/>
 | appmag_v=1.25<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR On-Line 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.|year=2002}}</ref> {{nowrap|(1.21–1.29<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)|journal=VizieR On-Line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|pages=02025|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009|display-authors=etal}}</ref>)}}
}}
{{Starbox character
 | class=A2&nbsp;Ia<ref name=baas25_1319>{{Cite journal |last1=Garrison |first1=R. F. |title=Anchor Points for the MK System of Spectral Classification |journal=[[Bulletin of the American Astronomical Society]] |volume=25 |page=1319 |year=1993 |bibcode=1993AAS...183.1710G |url=http://www.astro.utoronto.ca/~garrison/mkstds.html |access-date=2012-02-04 |archive-date=2019-06-25 |archive-url=https://web.archive.org/web/20190625094716/http://www.astro.utoronto.ca/~garrison/mkstds.html |url-status=dead }}</ref>
 | b-v=+0.09<ref name=ducati/>
 | u-b=−0.23<ref name=ducati/>
 | variable=[[Alpha Cygni variable|Alpha Cygni]]<ref name=gcvs/>
|type=[[Blue supergiant]]}}
{{Starbox astrometry
 | radial_v=−4.5<ref name=pulkovo>{{cite journal|bibcode=2006AstL...32..759G|title=Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system|journal=Astronomy Letters|volume=32|issue=11|pages=759–771|last1=Gontcharov|first1=G. A.|year=2006|doi=10.1134/S1063773706110065|arxiv = 1606.08053 |s2cid=119231169}}</ref>
 | prop_mo_ra=1.99<ref name=hipparcos/>
 | prop_mo_dec=1.95<ref name=hipparcos/>
 | parallax=2.31
 | p_error=0.32
 | parallax_footnote=<ref name=hipparcos/>
 | dist_ly={{val|1410|196|fmt=commas}} or {{val|2,615|215|fmt=commas}}
 | dist_pc={{val|433|60}}<ref name=hipparcos/> or {{val|802|66}}<ref name=schiller/>
 | absmag_v=−8.38<ref name=schiller/>
}}
{{Starbox detail
 | mass = {{val|15.5|0.8}}<ref name=Tetzlaff2011>{{Cite journal |last1=Tetzlaff |first1=N. |last2=Neuhäuser |first2=R. |last3=Hohle |first3=M. M. |date=2011-01-01 |title=A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun |journal=Monthly Notices of the Royal Astronomical Society |volume=410 |issue=1 |pages=190–200 |doi=10.1111/j.1365-2966.2010.17434.x |doi-access=free |arxiv=1007.4883 |bibcode=2011MNRAS.410..190T |issn=0035-8711}}</ref> or {{Val|19|4}}<ref name=Tetzlaff2011/>
 | radius = {{Val|117|14|19}}
<ref name=Baines2025>{{Cite journal |last1=Baines |first1=Ellyn K. |last2=Clark |first2=James H. |last3=Kingsley |first3=Bradley I. |last4=Schmitt |first4=Henrique R. |last5=Stone |first5=Jordan M. |date=2025-05-07 |title=Vintage NPOI: New and Updated Angular Diameters for 145 Stars |journal=The Astronomical Journal |language=en |volume=169 |issue=6 |pages=293 |doi=10.3847/1538-3881/adc930 |doi-access=free |bibcode=2025AJ....169..293B |issn=1538-3881}} Note: Full catalogue: [https://content.cld.iop.org/journals/1538-3881/169/6/293/revision1/ajadc930t7_mrt.txt]</ref> or {{Val|203|17}}<ref name=schiller>{{cite journal
  | last1=Schiller | first1=F.
  | last2=Przybilla | first2=N.
  | date=2008
  | title=Quantitative spectroscopy of Deneb
  | journal=[[Astronomy & Astrophysics]]
  | volume=479 | issue=3 | pages=849–858
  | arxiv=0712.0040
  | bibcode=2008A&A...479..849S
  | doi=10.1051/0004-6361:20078590
| s2cid=119225384
 }}</ref>
 | luminosity = {{val|55100|10000|fmt=commas}}<ref name="chesneau2"/> or {{Val|196000|32000|fmt=commas}}<ref name=schiller/>
 | age_myr = {{val|11.6|0.5}}<ref name=Tetzlaff2011/>
 | temperature = {{Val|8700|150|fmt=commas}}<ref>{{Cite journal |last1=Georgy |first1=Cyril |last2=Saio |first2=Hideyuki |last3=Meynet |first3=Georges |date=2021-06-01 |title=Blue supergiants as tests for stellar physics |url=https://www.aanda.org/articles/aa/abs/2021/06/aa40105-20/aa40105-20.html |journal=Astronomy & Astrophysics |language=en |volume=650 |pages=A128 |doi=10.1051/0004-6361/202040105 |arxiv=2104.06278 |bibcode=2021A&A...650A.128G |issn=0004-6361}}</ref>
 | rotational_velocity = {{Val|20|2}}<ref name=schiller/>
 | gravity = {{Val|1.10|0.05}}<ref name=schiller/>{{snd}}1.45<ref name=Albayrak>{{Cite journal |last=Albayrak |first=B. |date=2000-12-01 |title=A spectral analysis of Deneb (A2 Iae) |bibcode=2000A&A...364..237A |journal=Astronomy and Astrophysics |volume=364 |pages=237–248 |issn=0004-6361}}</ref>
 | metal_fe = −0.25<ref name=schiller/>
}}
{{Starbox catalog
 | names={{odlist | name=Arided | name2=Aridif | name3=Gallina | name4=Arrioph | B=α Cygni | F=50 Cygni | BD=+44°3541 | FK5=777 | HD=197345 | HIP=102098 | HR=7924 | SAO=49941 }}
}}
{{Starbox reference
 | Simbad=Deneb
}}
{{Starbox end}}

'''Deneb''' ({{IPAc-en|ˈ|d|ɛ|n|ɛ|b}}) is a [[blue supergiant]] [[star]] in the [[constellation]] of [[Cygnus (constellation)|Cygnus]]. It is the brightest star in the constellation and the [[List of brightest stars|19th brightest]] in the [[night sky]], with an [[apparent magnitude]] slightly varying between +1.21 and +1.29. Deneb is one of the vertices of the [[Asterism (astronomy)|asterism]] known as the [[Summer Triangle]] and the "head" of the [[Northern Cross (asterism)|Northern Cross]]. Its [[Bayer designation]] is '''α Cygni''', which is [[Latinisation of names|Latinised]] to '''Alpha Cygni''', abbreviated to '''Alpha Cyg''' or '''α Cyg'''. 

Deneb rivals [[Rigel]], a closer blue supergiant, as the most luminous [[first-magnitude star]]. However, its distance, and hence luminosity, is poorly known; its luminosity is estimated to be between 55,000 and 196,000 times [[Solar luminosity|that of the Sun]]. Distance estimates range from 1,400 to 2,600 light-years; assuming its highest value, it is the farthest star with an apparent magnitude brighter than 2.50.

==Nomenclature==

[[File:CygnusCC.jpg|thumb|left|upright|Deneb is the brighest star in the constellation of Cygnus (top)]]
''α Cygni'' (Latinised to ''Alpha Cygni'') is the star's [[Bayer designation|designation]] given by [[Johann Bayer]] in 1603. The traditional name ''Deneb'' is derived from the [[Arabic]] word for "tail", from the phrase ذنب الدجاجة ''Dhanab al-Dajājah'', or "tail of the hen".<ref name=allen/> The [[IAU Working Group on Star Names]] has recognised the name ''Deneb'' for this star, and it is entered in their Catalog of Star Names.<ref name="IAU-CSN">{{cite web |url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt |title=IAU Catalog of Star Names |website=University of Rochester |access-date=28 July 2016}}</ref>

''Denebadigege'' was used in the ''[[Alfonsine Tables]]'',<ref name=Kunitzsch86>
{{cite journal
 |last=Kunitzsch |first=Paul
 |date=1986
 |title=The Star Catalogue Commonly Appended to the Alfonsine Tables
 |journal=[[Journal for the History of Astronomy]]
 |volume=17 |issue=49 |pages=89–98
 |bibcode=1986JHA....17...89K
|doi=10.1177/002182868601700202
 |s2cid=118597258
 }}</ref> other variants include ''Deneb Adige'', ''Denebedigege'' and ''Arided''. This latter name was derived from ''Al Ridhādh'', a name for the constellation. [[Johann Bayer]] called it ''Arrioph'', derived from ''Aridf'' and ''Al Ridf'', 'the hindmost'  or ''Gallina''. German poet and author [[Philipp von Zesen|Philippus Caesius]] termed it ''Os rosae'', or ''Rosemund'' in German, or ''Uropygium'' – the parson's nose.<ref name=allen>
{{cite book
 |last=Allen
 |first=Richard Hinckley
 |date=1963
 |title=Star Names: Their Lore and Meaning
 |page=[https://archive.org/details/starnamestheirlo00alle/page/195 195]
 |edition=Reprint
 |publisher=[[Dover Publications]]
 |isbn=978-0-486-21079-7
 |url-access=registration
 |url=https://archive.org/details/starnamestheirlo00alle/page/195
 }}</ref> The names ''Arided'' and ''Aridif'' have fallen out of use.

An older traditional name is '''Arided''' {{IPAc-en|'|ær|ɪ|d|E|d}}, from the Arabic ''ar-ridf'' 'the one sitting behind the rider' (or just 'the follower'), perhaps referring to the other major stars of Cygnus, which were called ''al-fawāris'' 'the riders'.<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>

==Observation==
[[File:Summer triangle.png|left|thumb|upright=1.2|The [[Summer Triangle]]]]
The 19th [[List of brightest stars|brightest star]] in the night sky, Deneb [[culmination|culminates]] each year on October 23 at 6 PM and September 7 at 9 PM,<ref name="south2015">{{cite web |title=The Constellations : Part 3 Culmination Times|url=http://www.southastrodel.com/Page20502.htm|website=Southern Astronomical Delights|first=Andrew|last=James|date=2015-06-17 |access-date=2019-04-02}}</ref> corresponding to [[summer]] evenings in the [[northern hemisphere]].<ref name="summer" /> It never dips below the horizon at or above 45° north latitude, just grazing the northern horizon at its lowest point at such locations as [[Minneapolis]], [[Montreal|Montréal]] and [[Turin]]. In the [[Southern Hemisphere|southern hemisphere]], Deneb is not visible south of [[45th parallel south|45° parallel south]], so it just barely rises above the horizon in [[South Africa]], southern [[Australia]], and northern [[New Zealand]] during the southern winter.

Deneb is located at the tip of the [[Northern Cross (asterism)|Northern Cross]] asterism made up of the brightest stars in Cygnus, the others being [[Albireo]] (Beta Cygni), [[Gamma Cygni]], [[Delta Cygni]], and [[Epsilon Cygni]].<ref name="summer">{{cite journal|bibcode=1937ASPL....3...23S|title=Stars of the Summer Sky|journal=Astronomical Society of the Pacific Leaflets|volume=3|issue=102|pages=23|last1=Smith|first1=C. E.|year=1937}}</ref> It also lies at one [[Vertex (geometry)|vertex]] of the prominent and widely spaced [[Asterism (astronomy)|asterism]] called the [[Summer Triangle]], shared with the first-[[apparent magnitude|magnitude]] stars [[Vega]] in the constellation [[Lyra]] and [[Altair]] in [[Aquila (constellation)|Aquila]].<ref name="pasachoff2000">
{{Cite book
 |last1=Pasachoff |first1=J. M.
 |date=2000
 |title=A Field Guide to Stars and Planets
 |edition=4th
 |publisher=[[Houghton Mifflin]]
 |isbn=978-0-395-93431-9
}}</ref><ref name=upgren1998>
{{Cite book
 |last=Upgren |first=A. R.
 |date=1998
 |title=Night Has a Thousand Eyes: A Naked-Eye Guide to the Sky, Its Science, and Lore
 |publisher=[[Basic Books]]
 |isbn=978-0-306-45790-6
}}</ref> This outline of stars is the approximate shape of a [[right triangle]],<!--Image on side shows this is self-evident--> with Deneb located at one of the acute angles.

The [[stellar spectrum|spectrum]] of Alpha Cygni has been observed by astronomers since at least 1888, and by 1910 the variable [[radial velocity]] had become apparent. This led to the early suggestion by [[Edwin Brant Frost|E. B. Frost]] that this is a [[binary star]] system.<ref name=Lee1910>{{cite journal
 | title=Four stars having variable radial velocities
 | last=Lee | first=O. J.
 | journal=Astrophysical Journal
 | volume=31 | pages=176–179 | date=March 1910
 | doi=10.1086/141741 | bibcode=1910ApJ....31..176L
}}</ref> In 1935, the work of [[George Frederic Paddock|G. F. Paddock]] and others had established that this star was [[variable star|variable]] in luminosity with a dominant period of 11.7&nbsp;days and possibly with other, lower amplitude periods.<ref name=Abt1957>{{cite journal
 | title=The Variability of Supergiants
 | last=Abt | first=Helmut A.
 | journal=Astrophysical Journal
 | volume=126 | page=138 | date=July 1957
 | doi=10.1086/146379 | bibcode=1957ApJ...126..138A
}}</ref> By 1954, closer examination of the star's [[Calcium K line|calcium H and K lines]] showed a stationary core, which indicated the variable velocity was instead being caused by motion of the [[Stellar atmosphere|star's atmosphere]]. This variation ranged from +6 to −9&nbsp;km/s around the star's mean radial velocity.<ref>{{cite journal
 | title=The Stationary Calcium Lines of Alpha Cygni
 | last1=Struve | first1=Otto | last2=Huang | first2=S. S.
 | journal=Publications of the Astronomical Society of the Pacific
 | volume=66 | issue=392 | page=251 | date=October 1954
 | doi=10.1086/126710 | bibcode=1954PASP...66..251S
| s2cid=121714858 | doi-access=free }}</ref> Other, similar supergiants were found to have variable velocities, with this star being a typical member.<ref name=Abt1957/>

===Pole star===
Due to the [[Earth|Earth's]] [[axial precession]], Deneb will be an approximate [[pole star]] (7° off of the north celestial pole) at around [[List of future astronomical events#9th and 10th millennia|9800 AD]].<ref>{{cite web |title=Deneb |url=http://stars.astro.illinois.edu/sow/deneb.html |website=[[University of Illinois]] |first=James B. |last=Kaler |date=1998-06-19 |access-date=2018-04-25}}</ref> The north pole of [[Mars]] points to the midpoint of the line connecting Deneb and the star [[Alderamin]].<ref name="Barlow">
{{cite book |last=Barlow |first=N. G. |url=https://archive.org/details/marsintroduction00barl_258 |title=Mars: An introduction to its interior, surface and atmosphere |date=2008 |publisher=[[Cambridge University Press]] |isbn=978-0-521-85226-5 |page=[https://archive.org/details/marsintroduction00barl_258/page/n30 21] |url-access=limited}}</ref>
{| class="wikitable" style="margin: 1em auto 1em auto;"
! width="120" align="center"|Preceded by
! width="160" align="center"|[[Pole Star]]
! width="120" align="center"|Succeeded by
|-
|align="center"|'''[[Alderamin]]'''
|align="center"|8700 AD to 11000 AD
|align="center"|'''[[Delta Cygni]]'''
|}

==Physical characteristics==
[[File:Wide-field view of the Summer Triangle.jpg|thumb|upright=1.2|Wide-field view of the [[Summer Triangle]] and the [[Milky Way]]. Deneb is at the far left centre of the picture, at the end of the darker lane within the Milky Way.<!-- Not sure if you can find Deneb unless you have experience. -->]]
Deneb is a bluish-white star of [[stellar classification|spectral type]] A2Ia, classifying it as a [[blue supergiant]] star.<ref>{{Cite journal |last1=Wagle |first1=Gururaj A. |last2=Ray |first2=Alak |last3=Raghu |first3=Adarsh |date=2020-05-01 |title=Type IIP Supernova Progenitors III: Blue to Red Supergiant Ratio in Low Metallicity Models with Convective Overshoot |journal=The Astrophysical Journal |volume=894 |issue=2 |pages=118 |doi=10.3847/1538-4357/ab8bd5 |doi-access=free |arxiv=2004.14419 |bibcode=2020ApJ...894..118W |issn=0004-637X}}</ref> Since 1943, its [[stellar spectrum|spectrum]] has served as one of the stable references by which other stars are classified.<ref name=baas25_1319/> Its mass is estimated at 19 {{Solar mass|link=y}}. [[Stellar wind]]s causes matter to be lost at an average rate of {{Solar mass|8±3{{e|-7}}}} per year, 100,000 times the Sun's rate of mass loss or equivalent to about one [[Earth mass]] per 500 years.<ref>{{cite journal |bibcode=2002ApJ...570..344A |title=The Spectral Energy Distribution and Mass-Loss Rate of the A-Type Supergiant Deneb |journal=The Astrophysical Journal |volume=570 |issue=1 |pages=344 |last1=Aufdenberg |first1=J. P. |last2=Hauschildt |first2=P. H. |last3=Baron |first3=E. |last4=Nordgren |first4=T. E. |last5=Burnley |first5=A. W. |last6=Howarth |first6=I. D. |last7=Gordon |first7=K. D. |last8=Stansberry |first8=J. A. |year=2002 |doi=10.1086/339740 |arxiv=astro-ph/0201218 |s2cid=13260314}}</ref>

Deneb's distance from the Earth is uncertain. One estimate gives {{convert|802|pc|ly}} assuming Deneb is a member of the [[Cygnus OB7]] association.<ref name=schiller/> Another distance estimate using the [[bolometric magnitude]] implied by its [[effective temperature]] and [[surface gravity]] gives {{convert|762|pc|ly}}.{{Efn|1=From <math>d = 10^{\frac{\mu}{5}+1}</math>, where μ is the [[distance modulus]].}} The original derivation of a [[parallax]] using measurements from the astrometric satellite [[Hipparcos]] gave an uncertain result of {{val|1.01|0.57|ul=mas}}<ref name=aaa323_L49>{{Cite journal |last1=Perryman |first1=M. A. C. |last2=Lindegren |first2=L. |year=1997 |title=The Hipparcos Catalogue |journal=[[Astronomy and Astrophysics]] |volume=323 |pages=L49–L52  |bibcode=1997A&A...323L..49P |last3=Kovalevsky |first3=J. |last4=Hoeg |first4=E. |last5=Bastian |first5=U. |last6=Bernacca |first6=P. L. |last7=Crézé |first7=M. |last8=Donati |first8=F. |last9=Grenon |first9=M. |last10=Grewing |first10=M. |last11=Van Leeuwen |first11=F. |last12=Van Der Marel |first12=H. |last13=Mignard |first13=F. |last14=Murray |first14=C. A. |last15=Le Poole |first15=R. S. |last16=Schrijver |first16=H. |last17=Turon |first17=C. |last18=Arenou |first18=F. |last19=Froeschlé |first19=M. |last20=Petersen |first20=C. S. }}</ref><ref name=GSM>{{Cite book |last=Perryman |first=M. |date=2010 |title=The Making of History's Greatest Star Map |publisher=[[Springer-Verlag]] |doi=10.1007/978-3-642-11602-5 |isbn=978-3-642-11601-8 |series=Astronomers' Universe |url=https://cds.cern.ch/record/1338896 |type=Submitted manuscript |bibcode=2010mhgs.book.....P }}</ref> that was consistent with this distance. However, the 2007 re-analysis gives a much larger parallax resulting in a distance of {{Val|433|60|u=pc}}, or {{val|1410|196|fmt=commas|u=ly}}.<ref name=hipparcos/> The controversy over whether the direct Hipparcos measurements can be ignored in favour of a wide range of indirect stellar models and interstellar distance scales is similar to the better known [[Pleiades#Distance|situation with the Pleiades]].<ref name=hipparcos>{{cite journal |arxiv=0708.1752 |bibcode=2007A&A...474..653V |doi=10.1051/0004-6361:20078357 |title=Validation of the new Hipparcos reduction |journal=Astronomy and Astrophysics |volume=474 |issue=2 |pages=653–664 |year=2007 |last1=Van Leeuwen |first1=F. |s2cid=18759600}}</ref>

At its highest distance estimate, Deneb's [[absolute magnitude]] is estimated as −8.4, placing it among the visually brightest stars known, with an estimated luminosity of nearly {{solar luminosity|200,000|link=y}}.<ref>
{{Cite journal 
 |last1=van de Kamp |first1=P.
 |date=1953
 |title=The Twenty Brightest Stars
 |journal=[[Publications of the Astronomical Society of the Pacific]]
 |volume=65 |issue=382
 |pages=30
 |bibcode=1953PASP...65...30V
 |doi=10.1086/126523 
|doi-access=free
 }}</ref><ref>
{{Cite journal
 |last1=Lamers |first1=H. J. G. L. M.
 |last2=Stalio |first2=R.
 |last3=Kondo |first3=Y.
 |date=1978
 |title=A study of mass loss from the mid-ultraviolet spectrum of α Cygni (A2 Ia), β Orionis (B8 Ia), and η Leonis (A0 Ib)
 |journal=[[The Astrophysical Journal]]
 |volume=223 |pages=207
 |bibcode=1978ApJ...223..207L
 |doi=10.1086/156252
}}</ref> By the distance from Hipparcos parallax, Deneb has a luminosity of {{solar luminosity|55,000|link=y}}.<ref name="chesneau2">{{cite journal |last1=Chesneau |first1=O. |last2=Dessart |first2=L. |last3=Mourard |first3=D. |last4=Bério |first4=Ph. |last5=Buil |first5=Ch. |last6=Bonneau |first6=D. |last7=Borges Fernandes |first7=M. |last8=Clausse |first8=J. M. |last9=Delaa |first9=O. |last10=Marcotto |first10=A. |last11=Meilland |first11=A. |last12=Millour |first12=F. |last13=Nardetto |first13=N. |last14=Perraut |first14=K. |last15=Roussel |first15=A. |year=2010 |title=Time, spatial, and spectral resolution of the Hα line-formation region of Deneb and Rigel with the VEGA/CHARA interferometer |url=https://hal.archives-ouvertes.fr/hal-00501515 |journal=Astronomy and Astrophysics |volume=521 |pages=A5 |arxiv=1007.2095 |bibcode=2010A&A...521A...5C |doi=10.1051/0004-6361/201014509 |s2cid=10340205 |last16=Spang |first16=A. |last17=Stee |first17=P. |last18=Tallon-Bosc |first18=I. |last19=McAlister |first19=H. |last20=Ten Brummelaar |first20=T. |last21=Sturmann |first21=J. |last22=Sturmann |first22=L. |last23=Turner |first23=N. |last24=Farrington |first24=C. |last25=Goldfinger |first25=P. J.}}</ref>

Deneb is one of the most luminous first magnitude stars, that is, stars with a brighter apparent magnitude than 1.5. Deneb is also the most distant of the 30 [[List of brightest stars|brightest stars]].<ref>{{cite web
 | title=The 172 Brightest Stars | work=STARS
 | first=James B. | last=Kaler | date=2017
 | url=http://stars.astro.illinois.edu/sow/bright.html | access-date=2021-09-17
}}</ref> Based on its temperature and luminosity, and also on direct measurements of its tiny [[angular diameter]] (a mere 0.002 seconds of arc), Deneb appears to have a diameter about 100{{snd}}200 times [[Solar radius|that of the Sun]];<ref name="chesneau">{{cite journal |last1=Chesneau |first1=O. |last2=Dessart |first2=L. |last3=Mourard |first3=D. |last4=Bério |first4=Ph. |last5=Buil |first5=Ch. |last6=Bonneau |first6=D. |last7=Borges Fernandes |first7=M. |last8=Clausse |first8=J. M. |last9=Delaa |first9=O. |last10=Marcotto |first10=A. |last11=Meilland |first11=A. |last12=Millour |first12=F. |last13=Nardetto |first13=N. |last14=Perraut |first14=K. |last15=Roussel |first15=A. |year=2010 |title=Time, spatial, and spectral resolution of the Hα line-formation region of Deneb and Rigel with the VEGA/CHARA interferometer |url=https://hal.archives-ouvertes.fr/hal-00501515 |journal=Astronomy and Astrophysics |volume=521 |pages=A5 |arxiv=1007.2095 |bibcode=2010A&A...521A...5C |doi=10.1051/0004-6361/201014509 |s2cid=10340205 |last16=Spang |first16=A. |last17=Stee |first17=P. |last18=Tallon-Bosc |first18=I. |last19=McAlister |first19=H. |last20=Ten Brummelaar |first20=T. |last21=Sturmann |first21=J. |last22=Sturmann |first22=L. |last23=Turner |first23=N. |last24=Farrington |first24=C. |last25=Goldfinger |first25=P. J.}}</ref> if placed at the center of the [[Solar System]], Deneb would extend to the orbit of [[Mercury (planet)|Mercury]] or [[Earth's orbit|Earth]]. It is one of the [[List of largest stars|largest white 'A' spectral type stars known]].

===Evolutionary state===
Deneb spent much of its early life as an [[O-type main-sequence star]] of about {{solar mass|23}}, but it has now exhausted the [[hydrogen]] in its core and expanded to become a supergiant.<ref name=schiller/><ref name=georgy/> Stars in the mass range of Deneb eventually expand to become the most luminous [[red supergiants]], and within a few million years their cores will collapse producing a [[supernova]] explosion. It is now known that red supergiants up to a certain mass explode as the commonly seen [[type II supernova|type II-P supernova]]e, but more massive ones lose their outer layers to become hotter again.  Depending on their initial masses and the rate of mass loss, they may explode as [[yellow hypergiant]]s or [[luminous blue variable]]s, or they may become [[Wolf-Rayet star]]s before exploding in a [[Type Ib and Ic supernovae|type Ib or Ic supernova]]. Identifying whether Deneb is currently evolving towards a red supergiant or is currently evolving bluewards again would place valuable constraints on the classes of stars that explode as red supergiants and those that explode as hotter stars.<ref name=georgy>{{cite journal |bibcode=2014MNRAS.439L...6G |title=The puzzle of the CNO abundances of α Cygni variables resolved by the Ledoux criterion |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=439 |issue=1 |pages=L6–L10 |last1=Georgy |first1=Cyril |last2=Saio |first2=Hideyuki |last3=Meynet |first3=Georges |year=2014 |doi=10.1093/mnrasl/slt165 |doi-access=free |arxiv=1311.4744 |s2cid=118557550}}</ref>

Stars evolving red-wards for the first time are most likely fusing hydrogen in a shell around a [[helium]] core that has not yet grown hot enough to start fusion to [[carbon]] and [[oxygen]].  Convection has begun [[Stellar evolution#Mature stars#Mid-sized stars#Red-giant-branch phase|dredging]] up fusion products but these do not reach the surface. Post-red supergiant stars are expected to show those fusion products at the surface due to stronger convection during the red supergiant phase and due to loss of the obscuring outer layers of the star. Deneb is thought to be increasing its temperature after a period as a red supergiant, although current models do not exactly reproduce the surface elements showing in its spectrum.<ref name=georgy/> On the contrary, it is possible that Deneb has just left the main sequence and is evolving to a red supergiant phase, which is in agreement with estimates of its current mass, while its spectral composition can be explained by Deneb having been a rapidly rotating star during its main sequence phase.<ref name="schiller" />

===Variable star===
[[File:AlphaCygLightCurve.png|thumb|A [[Photometric_system#Photometric_letters|visual band]] [[light curve]] for Deneb, adapted from Yüce and Adelman (2019)<ref name="Yuca2019"/>]]
Deneb is the prototype of the [[Alpha Cygni variable|Alpha Cygni]] (α Cygni) [[variable star]]s,<ref name="Richardson2011" /><ref name="Yuca2019">{{cite journal
|last1=Yüce|first1=K.
|last2=Adelman |first2=S..J.
|title=On the variability of the A0 supergiants 9 Per, HR 1035, 13 Mon, Deneb, and HR 8020 as seen in FCAPT Strömgren photometry
|date=2019
|journal=New Astronomy
|volume=66
|pages=88–99
|doi=10.1016/j.newast.2018.07.002
|bibcode = 2019NewA...66...88Y|s2cid=126285732
}}</ref> whose small irregular amplitudes and rapid pulsations can cause its magnitude to vary anywhere between 1.21 and 1.29.<ref name="gscvquery">{{Cite web |url=http://www.sai.msu.su/gcvs/cgi-bin/search.cgi?search=alf+Cyg|title=GCVS Query forms|website=Sternberg Astronomical Institute|access-date=2019-01-07
}}</ref>  Its variable velocity discovered by Lee in 1910,<ref name=Lee1910/> but it was not formally placed as a unique class of variable stars until the 1985 4th edition of the General Catalogue of Variable Stars.<ref name="GCVS4">{{cite journal |bibcode=1996yCat.2139....0K |title=VizieR Online Data Catalog: General Catalog of Variable Stars, 4th Ed. (GCVS4) (/gcvs4Kholopov+ 1988) |journal=VizieR On-Line Data Catalog: II/139B. Originally Published in: Moscow: Nauka Publishing House (1985–1988) |volume=2139 |pages=0 |last1=Kholopov |first1=P. N. |last2=Samus' |first2=N. N. |last3=Frolov |first3=M. S. |last4=Goranskij |first4=V. P. |last5=Gorynya |first5=N. A. |last6=Kireeva |first6=N. N. |last7=Kukarkina |first7=N. P. |last8=Kurochkin |first8=N. E. |last9=Medvedeva |first9=G. I. |last10=Perova |first10=N. B.|date=1996}}</ref> The cause of the pulsations of Alpha Cygni variable stars are not fully understood, but their [[irregular variable|irregular nature]] seems to be due to [[Beat (acoustics)|beat]]ing of multiple pulsation periods. Analysis of radial velocities determined 16 different harmonic pulsation modes with periods ranging between 6.9 and 100.8 days.<ref name="Lucy1976"/> A longer period of about 800 days probably also exists.<ref name="Yuca2019" />

===Possible spectroscopic companion===
Deneb has been reported as a possible single line spectroscopic [[Binary star|binary]] with a period of about 850 days, where the spectral lines from the star suggest cyclical radial velocity changes.<ref name="Lucy1976">{{cite journal|bibcode=1976ApJ...206..499L|title=An analysis of the variable radial velocity of alpha Cygni|journal=Astrophysical Journal|volume=206|pages=499|last1=Lucy|first1=L. B.|year=1976|doi=10.1086/154405|doi-access=free}}</ref> Later investigations have found no evidence supporting the existence of a companion.<ref name="Richardson2011">{{cite journal |bibcode=2011AJ....141...17R |title=A Five-year Spectroscopic and Photometric Campaign on the Prototypical α Cygni Variable and A-type Supergiant Star Deneb |journal=The Astronomical Journal |volume=141 |issue=1 |pages=17 |last1=Richardson |first1=N. D. |last2=Morrison |first2=N. D. |last3=Kryukova |first3=E. E. |last4=Adelman |first4=S. J. |year=2011 |doi=10.1088/0004-6256/141/1/17 |arxiv=1009.5994 |s2cid=118300333}}</ref>

==Etymology and cultural significance==
Names similar to Deneb have been given to at least seven different stars, most notably [[Beta Ceti|Deneb Kaitos]], the brightest star in the constellation of [[Cetus]]; [[Delta Capricorni|Deneb Algedi]], the brightest star in [[Capricornus]]; and [[Denebola]], the second brightest star in [[Leo (constellation)|Leo]]. All these stars are referring to the tail of the animals that their respective constellations represent.

In Chinese, {{lang|zh|天津}} ({{lang|zh-Latn|Tiān Jīn}}), meaning ''[[Girl (Chinese constellation)|Celestial Ford]]'', refers to an asterism consisting of Deneb, [[Gamma Cygni]], [[Delta Cygni]], [[30 Cygni]], [[Nu Cygni]], [[Tau Cygni]], [[Upsilon Cygni]], [[Zeta Cygni]] and [[Epsilon Cygni]].<ref>{{cite book |author=陳久金|title=中國星座神話|url=https://books.google.com/books?id=0Vex0rYzdu8C|year=2005|publisher=五南圖書出版股份有限公司|isbn=978-986-7332-25-7}}</ref> Consequently, the [[Chinese star names|Chinese name]] for Deneb itself is {{lang|zh|天津四}} ({{lang|zh-Latn|Tiān Jīn sì}}, {{langx|en|the Fourth Star of the Celestial Ford}}).<ref>{{cite web|language=zh |url=http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_c_d.htm |title=香港太空館 - 研究資源 - 亮星中英對照表] |archive-url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_c_d.htm |archive-date=2008-10-25 | access-date=2019-01-09 | website=Hong Kong Space Museum}}</ref>

In the Chinese love story of [[Qi Xi]], Deneb marks the [[magpie]] bridge across the [[Milky Way]], which allows the separated lovers Niu Lang ([[Altair]]) and Zhi Nü ([[Vega]]) to be reunited on one special night of the year in late summer. In other versions of the story, Deneb is a fairy who acts as chaperone when the lovers meet.

===Namesakes===
[[USS Arided (AK-73)|USS ''Arided'']] was a [[United States Navy]] [[Crater class cargo ship|''Crater''-class cargo ship]] named after the star. [[SS Deneb|SS ''Deneb'']] was an Italian merchant vessel that bore this name from 1951 until she was scrapped in 1966.
==See also==
* [[List of bright stars]]
* [[Deneb Sector]]

== Notes ==
{{Notelist}}

==References==
{{Reflist|30em|refs=}}

{{Sky|20|41|25.9|+|45|16|49|1400}}
{{Stars of Cygnus}}
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[[Category:A-type supergiants]]
[[Category:Alpha Cygni variables]]
[[Category:Emission-line stars]]
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[[Category:Northern pole stars]]
[[Category:Cygnus (constellation)]]
[[Category:Bayer objects|Cygni, Alpha]]
[[Category:Durchmusterung objects|BD+44 3541]]
[[Category:Flamsteed objects|Cygni, 50]]
[[Category:Henry Draper Catalogue objects|197345]]
[[Category:Hipparcos objects|102098]]
[[Category:Bright Star Catalogue objects|7924]]
[[Category:Arabic words and phrases]]
[[Category:Population I stars]]
[[Category:Stars with proper names]]