delta Cancri
{{Short description|Orange giant star in the constellation Cancer}}
{{Starbox begin
| name=δ Cancri
}}
{{Starbox image
| image=
{{Location mark
|image=Cancer constellation map.svg|alt=|float=center|width=260
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=δ Cnc
|x=480|y=498
}}
|caption=Location of δ Cancri (circled)
}}
{{Starbox observe
| epoch = J2000.0
| constell = Cancer
| ra = {{RA|08|44|41.099}}{{Cite Gaia DR3|660136821288588416}}
| appmag_v = +3.94{{citation | display-authors=1
| last1=Johnson | 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 | postscript=. }}
}}
{{Starbox character
| variable =
}}
{{Starbox astrometry
| radial_v = {{Val|16.39|0.25}}{{citation | display-authors=1
| last1=Massarotti | first1=Alessandro | last2=Latham | first2=David W.
| last3=Stefanik | first3=Robert P. | last4=Fogel | first4=Jeffrey
| title=Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity
| journal=The Astronomical Journal
| volume=135 | issue=1 | pages=209–231 | date=January 2008
| doi=10.1088/0004-6256/135/1/209 | bibcode=2008AJ....135..209M | doi-access=free }}
| prop_mo_ra = −18.435
| prop_mo_dec = −227.813
| gal_lat = +32.8988
| gal_lon = 208.0259
| parallax = 23.8271
| p_error = 0.1853
| absmag_v = +0.843{{citation | display-authors=1
| last1=Soubiran | first1=C. | last2=Bienayme | first2=O.
| last3=Mishenina | first3=T. V. | last4=Kovtyukh | first4=V. V.
| title=Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants
| journal=Astronomy and Astrophysics | arxiv=0712.1370 | postscript=.
| volume=480 | issue=1 | pages=91–101 | date=March 2008
| bibcode=2008A&A...480...91S | doi=10.1051/0004-6361:20078788 | s2cid=16602121 }}
}}
{{Starbox detail
| mass = 1.71{{citation
| title=Abundances in the Local Region. I. G and K Giants
| last1=Luck | first1=R. Earle
| journal=The Astronomical Journal
| volume=150 | issue=3 | id=88 | pages=23 | date=September 2015
| doi=10.1088/0004-6256/150/3/88 | bibcode=2015AJ....150...88L
| arxiv=1507.01466 | s2cid=118505114 | postscript=. }}
| luminosity = {{val|59.5|1.4}}
| temperature = {{val|4684|27}}
}}
{{Starbox catalog
| names = {{odlist | name=Asellus Australis | B=δ Cnc | F=47 Cnc | BD=+18°2027 | FK5=326 | HD=74442 | HIP=42911 | HR=3461 | SAO=98087 | ADS=6967 | CCDM=08447+1809 | GC=12022 }}
}}
{{Starbox reference
| Simbad=del+Cnc
}}
{{Starbox end}}
Delta Cancri (δ Cancri, abbreviated Delta Cnc, δ Cnc) is a double star about 140 light-years from the Sun in the constellation of Cancer.
Its two main constituents are designated Delta Cancri A and B. A is itself a binary star whose components are Delta Cancri Aa (formally named Asellus Australis {{IPAc-en|ə|ˈ|s|ɛ|l|ə|s|_|ɔː|s|ˈ|t|r|eɪ|l|ɪ|s}}, the traditional name of the entire system){{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=16 December 2017}} and Ab.
The star system is 0.08 degree north of the ecliptic, so it can be occulted by the Moon and more rarely by planets; it is occulted (eclipsed) by the sun from about 31 July to 2 August.[http://in-the-sky.org/skymap.php?year=2019&month=4&day=9 In the Sky] Earth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present Thus the star can be viewed the whole night, crossing the sky at the start of February.
Nomenclature
δ Cancri (Latinised to Delta Cancri) is the system's Bayer designation. The designations of the two constituents Delta Cancri A and B, and those of A's components - Delta Cancri 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).{{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. }}
It bore the traditional name Asellus Australis which is Latin for "southern donkey colt". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN){{citation
| url=https://www.iau.org/science/scientific_bodies/working_groups/280/
| title=IAU Working Group on Star Names (WGSN)
| publisher=International Astronomical Union
| access-date=22 May 2016 | postscript=. }} to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.{{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}} It approved the name Asellus Australis for the component Delta Cancri Aa on 6 November 2016 and it is now so included in the List of IAU-approved Star Names. Together with Gamma Cancri, it formed the Aselli, flanking Praesepe.
As Arkū-sha-nangaru-sha-shūtu, which means "the southeast star in the Crab", it marked the 13th ecliptic station of the ancient Babylonians.Allen, Richard Hinckley, Star Names: Their Lore and Meaning, 1898.
In Chinese astronomy, Ghost ({{zh|c=鬼宿|p=Guǐ Xiù}}) refers to an asterism consisting of Theta Cancri, Eta Cancri, Gamma Cancri and Delta Cancri.{{cite book |author=陳久金 |script-title=zh:中國星座神話 |title=Zhōngguó Xīngzuò Shénhuà |trans-title=Chinese Constellation Mythology |url=https://books.google.com/books?id=0Vex0rYzdu8C&pg=394 |year=2005 |publisher=台灣古籍出版有限公司 |isbn=978-986-7332-25-7 |page=394}} Delta Cancri itself is known as the fourth star of Ghost ({{zh|c=鬼宿四|p=Guǐ Xiù sì}}).{{cite web |url=http://www.lcsd.gov.hk/CE/Museum/Space/zh_TW/web/spm/starshine/resources/constemyth/chinengstars/startable1.html |script-title=zh:亮星中英對照表 |trans-title=English-Chinese Glossary of Bright Stars |website=Hong Kong Space Museum |author= |language=zh |access-date=February 3, 2018| quote=Asellus Australis}}
Observations
Delta Cancri was involved in the first recorded occultation by Jupiter:
{{quote|"The most ancient observation of Jupiter which we are acquainted with is that reported by Ptolemy in book X, chap. iii (sic), of the Almagest, ...when the planet eclipsed the star known as (Delta) Cancri. This observation was made on September 3, B.C. 240, about 18h on the meridian of Alexandria."|Allen, 1898, quoting from Hind's The Solar System).}}
Delta Cancri also marks the famous open star cluster Praesepe (or the Beehive Cluster, also known as Messier 44). In ancient times M44 was used as a weather gauge as the following Greek rhyme from Aratos' Prognostica reveals:
{{quote|A murky manger with both stars
Shining unaltered is a sign of rain.
While if the northern Ass is dimmed
By vaporous shroud, he of the south gleam radiant,
Expect a south wind: the vaporous shroud and radiance
Exchanging stars harbinger Boreas.|Allen, 1898}}
The meaning of this verse is that if Asellus Borealis or Gamma CancrisKaler, 2009:{{cite web|url=http://www.astro.illinois.edu/~jkaler/sow/asellusbor.html |title=ASELLUS BOREALIS |url-status=dead |archive-url=https://web.archive.org/web/20110716072234/http://www.astro.illinois.edu/~jkaler/sow/asellusbor.html |archive-date=2011-07-16 }} is hidden by clouds, the wind will be from the south and that situation will be reversed if Asellus Australis is obscured. There is some doubt however as to the accuracy of this as Allen notes: "Our modern Weather Bureau would probably tell us that if one of these stars were thus concealed, the other also would be." (Allen, 1898)
But Delta Cancri also acts as more than just a dubious weather guide: it is a reliable signpost for finding the vividly red star X Cancri as Patrick Moore notes in his guidebook Stars of the Southern Skies:
{{quote|“In the same binocular field with Delta [Cancri] you will find one of the reddest stars in the sky: X Cancri. It is a semi-regular variable; at maximum it rises to magnitude 5 and it never falls below 7.3 so that it can always be seen with binoculars. It looks rather like a tiny glowing coal.”|Page 146, Moore, 1994.}}
Delta Cancri also marks the radiant of the Delta Cancrids meteor shower.
In 1876, the possibility of Delta Cancri having a companion star was proposed.{{cite journal |last1=Burnham |first1=S. W. |title=The companion to delta Cancri |journal=The Observatory |date=1878 |volume=2 |pages=60 |bibcode=1878Obs.....2...60B}}
References
{{Reflist}}
=Books=
- {{cite book|author=Richard H. Allen|title=Star Names: Their Lore and Meaning|url=https://books.google.com/books?id=vWDsybJzz7IC|date=28 February 2013|publisher=Courier Corporation|isbn=978-0-486-13766-7}}
- {{cite book|author=Robert Burnham|title=Burnham's Celestial Handbook, Volume One: An Observer's Guide to the Universe Beyond the Solar System|url=https://books.google.com/books?id=z3_CAgAAQBAJ&pg=PA340|date=15 April 2013|publisher=Courier Corporation|isbn=978-0-486-31902-5|pages=340–}}
- {{cite book|author=James B. Kaler|title=The Cambridge Encyclopedia of Stars|url=https://books.google.com/books?id=ZCB8QgAACAAJ|date=20 November 2006|publisher=Cambridge University Press|isbn=978-0-521-81803-2}}
- {{cite book|author1=Lloyd Motz|author2=Carol Nathanson|title=The constellations|url=https://archive.org/details/constellations00motz|url-access=registration|date=1 November 1988|publisher=Doubleday|isbn=9780385176002}}
- {{cite book|author=Patrick Moore|title=Atlas of the Universe|url=https://books.google.com/books?id=Iq6VQgAACAAJ|date=13 October 1998|publisher=Cambridge University Press|isbn=978-0-521-64210-1}}
- {{cite book|author=Patrick Moore|title=Stars of the Southern Skies|url=https://books.google.com/books?id=iCUbAAAACAAJ|year=1994|publisher=Penguin|isbn=978-0-14-024315-4}}
{{Stars of Cancer}}
{{DEFAULTSORT:Delta Cancri}}