{{short description|Triple star system in the constellation Vela}} {{Starbox begin | name=δ Velorum }} {{Starbox image | image= {{Location mark |image=Vela constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=12|mark_link=Delta Velorum|x=702|y=648 }} |caption=Location of δ Velorum (circled) }} {{Starbox observe 2s | constell = Vela | epoch = J2000 | component1 = δ Vel A | ra1 = {{RA|08|44|42.226}}<ref name=tycho/> | dec1 = {{DEC|−54|42|31.76}}<ref name=tycho/> | appmag_v1 = 1.95 - 2.43<ref name=vsx/> | component2 = δ Vel B | ra2 = {{RA|08|44|42.203}}<ref name=tycho/> | dec2 = {{DEC|−54|42|30.60}} | appmag_v2 = 5.54<ref name=kervella/> }} {{Starbox character | b-v = +0.04<ref name=clpl4_99/> | u-b = +0.07<ref name=clpl4_99/> }} {{Starbox character|no_heading=y | component = δ Vel A | type = Main sequence<ref name=merand/> | class = A1&nbsp;Va(n)<ref name=aj132_1_161/> | variable = Algol<ref name=gcvs/> }} {{Starbox character|no_heading=y | component = δ Vel B | type = Main sequence<ref name=merand/> | class = F7.5V<ref name=merand/> }} {{Starbox astrometry | radial_v = +2.2<ref name=wilson1953/> | prop_mo_ra = +28.99<ref name=aaa474_2_653/> | prop_mo_dec = −103.35<ref name=aaa474_2_653/> | parallax = 40.49 | p_error = 0.39 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = 0.02/3.60<ref name=aaa528_A21/> }} {{Starbox orbit | reference = <ref name=merand/> | primary = δ Vel A | name = δ Vel B | period = 143.2 | axis = 1.996 | eccentricity = 0.475 | inclination = 105.1 }} {{Starbox orbit | reference = <ref name=merand/> | primary = δ Vel Aa | name = δ Vel Ab | period_unitless = 45.1503 days | axis = 0.01651 | eccentricity = 0.287 | inclination = 89.04 }} {{Starbox detail | source = <ref name=merand/> | component1 = δ Vel Aa | mass = 2.43 | radius = 2.79–2.97 | luminosity = 67 | gravity = 3.78–3.90 | temperature = 9,440 | metal_fe = −0.33 | rotation = 1.05 days | rotational_velocity = 143.5 | age_myr = 400<ref name=aaa528_A21/>

| component2 = δ Vel Ab | mass2 = 2.27 | radius2 = 2.37–2.52 | luminosity2 = 51 | gravity2 = 3.99–4.10 | temperature2 = 9,830 | metal_fe2 = −0.33 | rotation2 = 0.85 days | rotational_velocity2 = 149.6 }} {{Starbox detail|no_heading = y | source = <ref name=merand/> | component1 = δ Vel B | mass = 1.35–1.46 | radius = 1.43 | luminosity = 3.5 | temperature = 6,600 | age_myr = }} {{Starbox catalog | names = Alsephina, CD−54°1788, GCTP&nbsp;2098.00, HD&nbsp;74956, HIP&nbsp;42913, HR&nbsp;3485, SAO&nbsp;236232, WDS 08447-5443 }} {{Starbox reference | Simbad=HD+74956 }} {{Starbox end}}

'''Delta Velorum''' ('''δ Velorum''', abbreviated '''Delta Vel''', '''δ Vel''') is a triple star system in the southern constellation of Vela, near the border with Carina, and is part of the False Cross. Based on parallax measurements, it is approximately {{Convert|80.6|ly|pc|abbr=off|lk=on}} from the Sun. It is one of the stars that at times lies near the south celestial pole due to precession.

δ Velorum consists of an eclipsing binary, designated Delta Velorum A, and a more distant third companion, Delta Velorum B. δ Velorum A's two components are themselves designated Aa (officially named '''Alsephina''' {{IPAc-en|æ|l|s|ɪ|'|f|ai|n|@}}, the traditional name for the entire system) and Ab.

== Nomenclature == [[File:Milky way - southern hemisphere contrast.jpg|thumb|left|upright=1.2|δ Velorum and the False Cross, lying across the Milky Way near the centre of this panorama]] ''δ Velorum'' (Latinised to ''Delta Velorum'') is the system's Bayer designation. The designations of the two constituents as ''Delta Velorum A'' and ''B'', and those of ''A''{{'s}} components—''Delta Velorum Aa'' and ''Ab''—derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).<ref name="planetnaming"/>

Delta Velorum bore the traditional name ''Alsafinah'', which stems from the Arabic name ''al-safīnah'' meaning "the ship", referring to the ancient Greek constellation Argo Navis, the ship of the Argonauts. It was first used in a 10th-century Arabic translation of the ''Almagest'', written by the Greek astronomer Ptolemy in the second century AD. Although the name originally referred to an entire constellation, it was assigned to this particular bright star at least as early as 1660, when it appeared in Andreas Cellarius's renowned ''Harmonia Macrocosmica'', a magnificently illustrated 17th-century Dutch book about the cosmos.<ref name="iau1707"/> In 2016, the IAU organized a Working Group on Star Names (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.<ref name=TriRpt18/> It approved the name ''Alsephina'' for the component δ Velorum Aa on 5&nbsp;September 2017 and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>

The False Cross is an asterism formed of Delta and Kappa Velorum along with Iota Carinae and Epsilon Carinae. It is so called because it is sometimes mistaken for the Southern Cross, causing errors in astronavigation.<ref name=moore/>

In Chinese, {{lang|zh|天社}} ({{lang|zh-Latn|Tiān Shè}}), meaning ''Celestial Earth God's Temple'', refers to an asterism consisting of Delta Velorum, Gamma<sup>2</sup> Velorum, Kappa Velorum and b Velorum.<ref name="zh"/> Consequently, Delta Velorum itself is known as {{lang|zh|天社三}} ({{lang|zh-Latn|Tiān Shè sān}}), "the Third Star of Celestial Earth God's Temple".<ref name="lcsd"/> In a different Chinese view, this star appears in an asterism with the given name of ''Koo She'' (Chinese: 弧矢, hú shǐ, "Bow and Arrow"), comprising Delta Velorum, Omega Carinae and stars from Canis Major.<ref name="hinkley63"/>

==Stellar system== thumb|left|Relative positions and separations of components A, B, C and D of δ Velorum Delta Velorum is a triple star system. The outer components, δ Velorum A and B, have a wide orbit with a 143-year period. The primary component A has an apparent magnitude of 2.00, while the secondary B is magnitude 5.54, with a combined magnitude measured at 1.96.<ref name=hr/> As of 2013, the two stars were separated by 0.6", but they have an eccentric orbit and their average separation over the whole orbit is nearly 2".<ref name=merand/>

In 1978 the primary component was reported to be a spectroscopic binary in the Proceedings of the Australian Astronomical Observatory, and this was confirmed by the ''Hipparcos'' satellite.<ref name="Otero2000"/>

[[File:DeltaVelLightCurve.png|thumb|left|A white-light light curve for Delta Velorum, adapted from Pribulla ''et al.'' (2011)<ref name=aaa528_A21/>]] In 2000 it was announced that the inner components Aa and Ab form an eclipsing binary, having an orbital period of 45.15 days and an eccentricity of 0.230.<ref name=aaa528_A21/> The semi-major axis as their orbit corresponds to a mean separation of {{val|90.61|ul=R_solar}}.<ref name=eker/> Observations of variability in the Delta Velorum system were made independently by ground-based astronomers and the ''Galileo'' spaceprobe at Jupiter.<ref name="Otero2000"/> The inner pair were resolved using interferometry in 2007, and then using NACO adaptive optics with the Very Large Telescope. Photometry of the components of δ Velorum A gives apparent visual magnitudes of 2.33 and 3.44.<ref name=kervella/> The precise orbits allow a dynamical parallax of {{val|39.8|0.4|u=mas}} to be derived, representing a distance of 25.1 parsecs.<ref name=merand/>

Another binary system is located at an angular separation of 69 arcseconds from δ Velorum, sometimes referred to as δ Velorum C and D. The pair is composed of an 11th-magnitude star and a 13th-magnitude star, which are 6 arcseconds apart. The two stars, with approximate spectral types of G8V and K0V, are expected to be more distant than δ Velorum and not physically associated.<ref name=kellerer/>

HD 76653 is a probable (96% chance) co-moving companion; the two have an estimated physical separation of {{Cvt|0.6605|pc|ly|1|order=flip}} with similar proper motions.<ref name=Shaya2011/> Both are likely members of the Ursa Major Moving Group.<ref name=Fuhrmann2012/>

== Physical properties == The brightnesses of the three stars have been measured at visual and infrared wavelengths using adaptive optics. The physical properties implied by their surface brightnesses and colour indices suggests spectral types of A2IV, A4V and F8V, respectively.<ref name=kervella/>

More precise physical properties for the stars can be calculated using accurate orbital parameters. Both members of the spectroscopic binary Delta Velorum A are slightly evolved stars that are still on the main sequence.<ref name=aaa528_A21/> Component Aa has 2.5 times the mass of the Sun, 2.6 times the Sun's radius, and is radiating 56 times the luminosity of the Sun at an effective temperature of {{Val|9470|fmt=commas|ul=K}}. Component Ab is only slightly smaller, with 2.4 times the Sun's mass and radius, with a luminosity of 47 times the Sun and an effective temperature of 9,370&nbsp;K.<ref name=aaa528_A21/>

Both stars are rotating rapidly and are significantly oblate, with equatorial radii larger than their polar radii. Gravity darkening results in their effective temperatures at the pole being higher than that of the equator. For component Aa, the polar radius and temperature are {{solar radius|2.79}} and 10,100&nbsp;K, respectively, while the equatorial radius and temperature are {{solar radius|2.97}} and 9,700&nbsp;K, respectively. For component Ab, the corresponding polar values are {{solar radius|2.37}} and 10,120&nbsp;K, and the equatorial values are {{solar radius|2.52}} and 9,560&nbsp;K.<ref name=merand/> This results in the star being brighter when seen along their axes of rotation and less bright when observed at their equators. From Earth, the pair is observed nearly equatorially and the absolute visual magnitude is +0.02; from a different direction the absolute magnitude would be −0.138 or less.<ref name=aaa528_A21/>

Delta Velorum B is a smaller main-sequence star, with a mass of about {{solar mass|1.4}}, a temperature of 6,600&nbsp;K, a radius of {{solar radius|1.43}}, and a bolometric luminosity of {{solar luminosity|3.5}}.<ref name=merand/>

==Southern pole star== {{main|South star}} The south celestial pole will pass close to Delta Velorum around 9000 AD because of precession.<ref name=JK/>

{{-}} == References == <references> <ref name=aaa474_2_653>{{cite journal | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}</ref>

<ref name=aj132_1_161>{{cite journal | display-authors=1 | last1=Gray | first1=R. O. | last2=Corbally | first2=C. J. | last3=Garrison | first3=R. F. | last4=McFadden | first4=M. T. | last5=Bubar | first5=E. J. | last6=McGahee | first6=C. E. | last7=O'Donoghue | first7=A. A. | last8=Knox | first8=E. R. | title=Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample | journal=The Astronomical Journal | volume=132 | issue=1 | pages=161–170 |date=July 2006 | doi=10.1086/504637 | bibcode=2006AJ....132..161G | arxiv=astro-ph/0603770 | s2cid=119476992 }}</ref>

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<ref name=clpl4_99>{{cite journal | last1=Johnson | display-authors=1 | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99 | year=1966 | bibcode=1966CoLPL...4...99J }}</ref>

<ref name="hinkley63">{{cite book | first=Richard Hinckley | last=Allen | author-link=Richard Hinckley Allen | year=1963 | title=Star Names: Their Lore and Meaning | edition=Revised | publisher=Dover Publications | location=New York | isbn=0-486-21079-0 | page=[https://archive.org/details/starnamestheirlo00alle/page/73 73] | url-access=registration | url=https://archive.org/details/starnamestheirlo00alle/page/73 }}</ref>

<ref name=aaa528_A21>{{cite journal | display-authors=1 | last1=Pribulla | first1=T. | title=The nearby eclipsing stellar system δ Velorum. II. First reliable orbit for the eclipsing pair | last2=Merand | first2=A. | last3=Kervella | first3=P. | last4=Vaňko | first4=M. | last5=Stevens | first5=I. R. | last6=Chini | first6=R. | last7=Hoffmeister | first7=V. | last8=Stahl | first8=O. | last9=Berndt | first9=A. | last10=Mugrauer | first10=M. | last11=Ammler-von Eiff | first11=M. | journal=Astronomy & Astrophysics | volume=528 | page=A21 |date=April 2011 | doi=10.1051/0004-6361/201016227 | bibcode=2011A&A...528A..21P |arxiv = 1012.5886 | s2cid=119261896 }}</ref>

<ref name="Otero2000">{{cite journal | first1=Fieseler & Lloyd | last1=Otero | year=2000 | title=Delta Velorum is an Eclipsing Binary | journal=Information Bulletin on Variable Stars | volume=4999 | pages=1 |publisher=IBVS 4999 | bibcode=2000IBVS.4999....1O | last2=Fieseler | first2=Paul D. | last3=Lloyd | first3=Christopher }}</ref>

<ref name=Fuhrmann2012>{{cite journal | title=Multiplicity among F-type Stars | journal=The Astrophysical Journal Supplement | volume=203 | issue=2 | pages=30 | year=2012 | last1=Fuhrmann | first1=K | last2=Chini | first2=R | bibcode=2012ApJS..203...30F | doi=10.1088/0067-0049/203/2/30 | doi-access=free }}</ref>

<ref name=Shaya2011>{{cite journal | last1=Shaya | first1=Ed J. | last2=Olling | first2=Rob P. | title=Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue | journal=The Astrophysical Journal Supplement | volume=192 | issue=1 | page=2 | date=January 2011 | doi=10.1088/0067-0049/192/1/2 | bibcode=2011ApJS..192....2S | arxiv=1007.0425 | s2cid=119226823 }}</ref>

<ref name=merand>{{cite journal|bibcode=2011A&A...532A..50M|arxiv=1106.2383|title=The nearby eclipsing stellar system δ Velorum. III. Self-consistent fundamental parameters and distance|journal=Astronomy & Astrophysics|volume=532|pages=A50|last1=Mérand|first1=A|last2=Kervella|first2=P|last3=Pribulla|first3=T|last4=Petr-Gotzens|first4=M. G|last5=Benisty|first5=M|last6=Natta|first6=A|last7=Duvert|first7=G|last8=Schertl|first8=D|last9=Vannier|first9=M|year=2011|doi=10.1051/0004-6361/201116896|s2cid=118567393}}</ref>

<ref name=tycho>{{cite journal|bibcode=2002A&A...384..180F|title=The Tycho double star catalogue|journal=Astronomy and Astrophysics|volume=384|pages=180–189|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.|year=2002|doi=10.1051/0004-6361:20011822|doi-access=free}}</ref>

<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>

<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars | publisher=IAU.org | access-date=16 December 2017 | archive-date=10 March 2025 | archive-url=https://web.archive.org/web/20250310063743/https://www.iau.org/public/themes/naming_stars/ | url-status=dead }}</ref>

<ref name=JK>{{cite web | url=http://stars.astro.illinois.edu/sow/deltavel.html | title=Delta Velorum | work=Stars | publisher=University of Illinois | access-date=2012-08-04 | first1=James B. | last1=Kaler }}</ref>

<ref name="planetnaming">{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }}</ref>

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<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN) | access-date=22 May 2016 | archive-date=10 June 2016 | archive-url=https://web.archive.org/web/20160610172014/https://www.iau.org/science/scientific_bodies/working_groups/280/ | url-status=dead }}</ref>

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<ref name=zh>{{in lang|zh}} ''中國星座神話'', written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}.</ref>

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<ref name=hr>{{cite journal|bibcode=1995yCat.5050....0H|title=VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)|journal=VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H|volume=5050|pages=0|last1=Hoffleit|first1=D.|last2=Warren|first2=W. H.|year=1995}}</ref>

<ref name=eker>{{cite journal|bibcode=2014PASA...31...24E|title=The Catalogue of Stellar Parameters from the Detached Double-Lined Eclipsing Binaries in the Milky Way|journal=Publications of the Astronomical Society of Australia|volume=31|article-number=e024|last1=Eker|first1=Z|last2=Bilir|first2=S|last3=Soydugan|first3=F|last4=Gökçe|first4=E. Yaz|last5=Soydugan|first5=E|last6=Tüysüz|first6=M|last7=Şenyüz|first7=T|last8=Demircan|first8=O|year=2014|doi=10.1017/pasa.2014.17|arxiv=1403.1583|s2cid=119238300}}</ref>

<ref name=kellerer>{{cite journal|bibcode=2007A&A...469..633K|arxiv=astro-ph/0703798|title=Interferometric observations of the multiple stellar system δ Velorum|journal=Astronomy and Astrophysics|volume=469|issue=2|pages=633|last1=Kellerer|first1=A|last2=Petr-Gotzens|first2=M. G|last3=Kervella|first3=P|last4=Coudé Du Foresto|first4=V|year=2007|doi=10.1051/0004-6361:20077079|s2cid=14736172}}</ref>

<ref name=kervella>{{cite journal|bibcode=2009A&A...493..107K|arxiv=0811.1682|title=The nearby eclipsing stellar system δ Velorum . I. Origin of the infrared excess from VISIR and NACO imaging|journal=Astronomy and Astrophysics|volume=493|pages=107–114|last1=Kervella|first1=P|last2=Thévenin|first2=F|last3=Petr-Gotzens|first3=M. G|year=2009|issue=1|doi=10.1051/0004-6361:200810565|s2cid=15408237}}</ref>

<ref name=vsx>{{cite web |url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=37805 |title=Delta Vel |access-date=2022-07-19 | publisher=AAVSO |website=International Variable Star Index }}</ref>

<ref name=TriRpt18>{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015–2018) – Star Names | access-date=2018-07-14 | archive-date=2019-08-23 | archive-url=https://web.archive.org/web/20190823174756/https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | url-status=dead }}</ref> </references>

== External links == *{{WikiSky|Delta Velorum}} {{Sky|08|44|42.22658|-|54|42|31.7493|79.745234}}

{{Stars of Vela}}

{{Authority control}}

Category:A-type main-sequence stars Category:F-type main-sequence stars Category:Algol variables Category:Triple star systems Category:Ursa Major moving group Velorum, Delta Category:Vela (constellation) CD-54 2351 074956 042913 3485 Alsephina Category:Brightest stars