Delta Cancri
  | |
| Observation data EpochJ2000.0EquinoxJ2000.0 | |
|---|---|
| Constellation | Cancer |
| Right ascension | 08h44m41.099s[1] |
| Declination | +18° 09′ 15.509″[1] |
| Apparent magnitude(V) | +3.94[2] |
| Characteristics | |
| Spectral type | K0 III[3] |
| U−Bcolor index | +0.99[2] |
| B−Vcolor index | +1.08[2] |
| Astrometry | |
| Radial velocity(Rv) | 16.39±0.25[4]km/s |
| Proper motion(μ) | RA:−18.435mas/yr[1] Dec.:−227.813mas/yr[1] |
| Parallax(π) | 23.8271 ± 0.1853mas[1] |
| Distance | 137 ± 1ly (42.0 ± 0.3pc)[1] |
| Absolute magnitude(MV) | +0.843[5] |
| Details | |
| Mass | 1.71[3]M☉ |
| Radius | 11.7±0.13[6]R☉ |
| Luminosity | 59.5±1.4[6]L☉ |
| Surface gravity(logg) | 2.59[6]cgs |
| Temperature | 4684±27[6]K |
| Metallicity[Fe/H] | −0.03[6]dex |
| Rotational velocity(vsini) | 2.8[4]km/s |
| Age | 2.45[3]Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta Cancri(δ Cancri,abbreviatedDelta Cnc,δ Cnc) is adouble starabout 140light-yearsfrom the Sun in theconstellationofCancer.
Its two main constituents are designated Delta Cancri A and B. A is itself abinary starwhose components are Delta Cancri Aa (formally namedAsellus Australis/əˈsɛləsɔːsˈtreɪlɪs/,the traditional name of the entire system)[7]and Ab.
The star system is 0.08 degree north of theecliptic,so it can beoccultedby theMoonand more rarely byplanets;it is occulted (eclipsed) by the sun from about 31 July to 2 August.[8]Thus the star can be viewed the whole night, crossing the sky at the start of February.
Nomenclature
[edit]δ Cancri(LatinisedtoDelta Cancri) is the system'sBayer designation.The designations of the two constituentsDelta Cancri AandB,and those ofA'scomponents -Delta Cancri AaandAb- derive from the convention used by the Washington Multiplicity Catalog (WMC) formultiple star systems,and adopted by theInternational Astronomical Union(IAU).[9]
It bore the traditional nameAsellus Australiswhich isLatinfor "southerndonkeycolt ".[10]In 2016, theInternational Astronomical Unionorganized aWorking Group on Star Names(WGSN)[11]to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entiremultiple systems.[12]It approved the nameAsellus Australisfor the component Delta Cancri Aa on 6 November 2016 and it is now so included in the List of IAU-approved Star Names.[7]Together withGamma Cancri,it formed theAselli,flankingPraesepe.[10]
AsArkū-sha-nangaru-sha-shūtu,which means "the southeast star in the Crab", it marked the 13th ecliptic station of the ancientBabylonians.[10]
InChinese astronomy,Ghost(Chinese:Quỷ túc;pinyin:Guǐ Xiù) refers to anasterismconsisting ofTheta Cancri,Eta Cancri,Gamma Cancriand Delta Cancri.[13]Delta Cancri itself is known as the fourth star of Ghost (Chinese:Quỷ túc tứ;pinyin:Guǐ Xiù sì).[14]
Observations
[edit]Delta Cancri was involved in the first recorded occultation by Jupiter:
"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 fromHind's The Solar System).
Delta Cancri also marks the famous open star cluster Praesepe (or theBeehive Cluster,also known as Messier 44). In ancient times M44 was used as a weather gauge as the following Greek rhyme from Aratos'Prognosticareveals:
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 Cancris[15]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 guidebookStars of the Southern Skies:
“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 theDelta Cancridsmeteor shower.
In 1876, the possibility of Delta Cancri having acompanionstar was proposed.[16]
References
[edit]- ^abcdeVallenari, A.; et al. (Gaia collaboration) (2023)."GaiaData Release 3. Summary of the content and survey properties ".Astronomy and Astrophysics.674:A1.arXiv:2208.00211.Bibcode:2023A&A...674A...1G.doi:10.1051/0004-6361/202243940.S2CID244398875. Gaia DR3 record for this sourceatVizieR.
- ^abcJohnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars",Communications of the Lunar and Planetary Laboratory,4(99): 99,Bibcode:1966CoLPL...4...99J.
- ^abcLuck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants",The Astronomical Journal,150(3): 23,arXiv:1507.01466,Bibcode:2015AJ....150...88L,doi:10.1088/0004-6256/150/3/88,S2CID118505114,88.
- ^abMassarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity",The Astronomical Journal,135(1): 209–231,Bibcode:2008AJ....135..209M,doi:10.1088/0004-6256/135/1/209
- ^Soubiran, C.; et al. (March 2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants",Astronomy and Astrophysics,480(1): 91–101,arXiv:0712.1370,Bibcode:2008A&A...480...91S,doi:10.1051/0004-6361:20078788,S2CID16602121.
- ^abcdeBaines, Ellyn K.; Armstrong, J. Thomas; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David; Nisley, Ishara; Sanborn, Jason; Schmitt, Henrique R.; Belle, Gerard T. van (October 2021)."Angular Diameters and Fundamental Parameters of Forty-four Stars from the Navy Precision Optical Interferometer".The Astronomical Journal.162(5): 198.arXiv:2211.09030.Bibcode:2021AJ....162..198B.doi:10.3847/1538-3881/ac2431.ISSN1538-3881.
- ^ab"Naming Stars".IAU.org.Retrieved16 December2017.
- ^In the SkyEarth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present
- ^Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets".arXiv:1012.0707[astro-ph.SR].
- ^abcAllen, Richard Hinckley,Star Names: Their Lore and Meaning,1898.
- ^IAU Working Group on Star Names (WGSN),International Astronomical Union,retrieved22 May2016.
- ^"WG Triennial Report (2015-2018) - Star Names"(PDF).p. 5.Retrieved2018-07-14.
- ^Trần cửu kim (2005).Zhōngguó Xīngzuò ShénhuàTrung quốc tinh tọa thần thoại[Chinese Constellation Mythology]. Đài loan cổ tịch xuất bản hữu hạn công tư. p. 394.ISBN978-986-7332-25-7.
- ^Lượng tinh trung anh đối chiếu biểu[English-Chinese Glossary of Bright Stars].Hong Kong Space Museum(in Chinese).RetrievedFebruary 3,2018.
Asellus Australis
- ^Kaler, 2009:"ASELLUS BOREALIS".Archived fromthe originalon 2011-07-16.
- ^Burnham, S. W. (1878). "The companion to delta Cancri".The Observatory.2:60.Bibcode:1878Obs.....2...60B.
Books
[edit]- Richard H. Allen (28 February 2013).Star Names: Their Lore and Meaning.Courier Corporation.ISBN978-0-486-13766-7.
- Robert Burnham (15 April 2013).Burnham's Celestial Handbook, Volume One: An Observer's Guide to the Universe Beyond the Solar System.Courier Corporation. pp. 340–.ISBN978-0-486-31902-5.
- James B. Kaler (20 November 2006).The Cambridge Encyclopedia of Stars.Cambridge University Press.ISBN978-0-521-81803-2.
- Lloyd Motz; Carol Nathanson (1 November 1988).The constellations.Doubleday.ISBN9780385176002.
- Patrick Moore (13 October 1998).Atlas of the Universe.Cambridge University Press.ISBN978-0-521-64210-1.
- Patrick Moore (1994).Stars of the Southern Skies.Penguin.ISBN978-0-14-024315-4.
