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Zeta Cancri

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ζ Cancri A/B/C
Location of ζ Cancri (circled)
Observation data
EpochJ2000.0EquinoxJ2000.0
Constellation Cancer
Right ascension 08h12m12.7s
Declination +17° 38′ 52″
Apparent magnitude(V) +5.58/+5.99/+6.12
Characteristics
Evolutionary stage main-sequence star
Spectral type F7V + F9V + G0V
Other designations
Tegmen, Tegmine, 16 Cancri,HR3208/3209/3210,HD68257/68255/68256,BD+18°1867,HIP40167,SAO97645/97646, GC 11142/11141,ADS6650,CCDMJ08123+1738,WDS08122+1739

Zeta Cancri(ζ Cancri,abbreviatedZeta Cnc,ζ Cnc) is a multiplestar systemin theconstellationofCancer.It is approximately 83.4light-yearsfromEarth,and has a combinedapparent magnitudeof +4.67. Since it is near theecliptic,it can beoccultedby theMoonand, very rarely, byplanets.

The system is constituted as follows:[1]

  • Abinary pairdesignated Zeta1Cancri or, alternatively, Zeta Cancri AB, the two components of which are themselves designated Zeta1Cancri A or, simply, Zeta Cancri A (formally also namedTegmine/ˈtɛɡmɪniː/,the traditional name of the Zeta Cancri system)[2]and Zeta1/Zeta Cancri B.
  • Atriple star systemdesignated Zeta2Cancri or alternatively Zeta Cancri C, consisting of a single star primary, designated Zeta2/Zeta Cancri Ca, together with a secondary binary pair, designated Zeta2/Zeta Cancri Cb. The binary pair's two components are themselves designated Zeta2/Zeta Cancri Cb1 and Cb2.

Nomenclature[edit]

ζ Cancri(LatinisedtoZeta Cancri) is the system'sBayer designation;ζ1Cancriandζ2Cancrithose of its two constituents. The designations of the two constituents asζ Cancri ABandC,and those of their components—ζ Cancri A,B,Ca,Cb,Cb1andCb2—derive from the convention used by the Washington Multiplicity Catalog (WMC) formultiple star systems,and adopted by theInternational Astronomical Union(IAU).[3]

Considerable confusion had developed concerning the catalogue identities of the three bright stars; correct correspondences were worked out by Griffin:[4]

Component HR HD SAO HIP
ζ Cancri A 3208 68257 97645 40167
ζ Cancri B 3209 68255
ζ Cancri C 3210 68256 97646

Zeta Cancribore the traditional nameTegmine(Tegmen) "the shell (of the crab)".[citation needed]In 2016, theInternational Astronomical Unionorganized aWorking Group on Star Names(WGSN)[5]to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entiremultiple systems.[6]It approved the nameTegminefor the componentZeta1Cancri Aon 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[2]

InChinese,Mực nước(Shuǐ Wèi), meaningWater Level,refers to anasterismconsisting of Zeta Cancri,6 Canis Minoris,11 Canis Minorisand8 Cancri.[7]Consequently, Zeta Cancri itself is known asMực nước bốn(Shuǐ Wèi sì,English:the Fourth Star of Water Level).[8]

Properties[edit]

Zeta Cancri can be resolved as a binary star in small telescopes. Its binary nature was discovered in 1756 byTobias Mayer.William Herschelresolved the two components that make up Zeta1Cancri in 1781. As early as 1831,John Herschelnoticedperturbationsin Zeta2Cancri'sorbitaround Zeta1;this ledOtto Wilhelm von Struve,in 1871, to postulate a fourth, unseen, component which orbited closely the visible member of Zeta2.[4]Later observations have resolved this fourth component and have indicated that there may be one or two more unobserved components.[9][10]

Zeta1and Zeta2Cancri are 5.06arcsecondsapart. These two star systems orbit around their commoncentre of massonce every 1,100 years.

Zeta1Cancri[edit]

The two components are both yellow-whitemain-sequencedwarfs ofspectral class F.Theapparent magnitudesof A and B are +5.58 and +5.99, respectively. They are separated, as of 2008, by 1arcsecond,requiring a large telescope to resolve them, but this separation will increase until the year 2020. They complete one orbit every 59.6 years.[11]The estimated masses for the pair are 1.28 and 1.18solar masses,respectively.

Zeta2Cancri[edit]

Zeta Cancri Ca is the brightest of the three components, having an apparent magnitude of +6.12. It appears to be a yellowG-type star,often reported as G5V, but now thought to be earlier, probably G0V. This star has around 1.15solar masses.[12]The tenth magnitude Zeta Cancri Cb is a close pair ofred dwarfs.The separation between Ca and Cb is approximately 0.3arcsecond,and theirorbital periodis 17 years.

References[edit]

  1. ^"Displaying next number in catalog HIP => 40167".Multiple Star Catalog.Archived fromthe originalon 2018-02-18.Retrieved2018-02-18.
  2. ^ab"Naming Stars".IAU.org.Retrieved16 December2017.
  3. ^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].
  4. ^abGriffin, R. F. (2000). "Spectroscopic Binary Orbits from Photoelectrical Radial Velocities: Paper 150: ζ Cancri C".The Observatory.120:1–47.Bibcode:2000Obs...120....1G.
  5. ^IAU Working Group on Star Names (WGSN),International Astronomical Union,retrieved22 May2016.
  6. ^"WG Triennial Report (2015-2018) - Star Names"(PDF).p. 5.Retrieved2018-07-14.
  7. ^(in Chinese)Trung Quốc chòm sao thần thoại,written by trần lâu kim. Published by Đài Loan thư phòng xuất bản công ty hữu hạn, 2005,ISBN978-986-7332-25-7.
  8. ^(in Chinese)Hong Kong vũ trụ quán - nghiên cứu tài nguyên - lượng tinh trung anh đối chiếu biểuArchivedAugust 19, 2010, at theWayback Machine,Hong Kong Space Museum. Accessed on line November 23, 2010.
  9. ^Hutchings, J. B.; Griffin, R. F.; Menard, F. (2000). "Direct observation of the fourth star in the Zeta Cancri system".Publications of the Astronomical Society of the Pacific(abstract).112(772): 833–836.arXiv:astro-ph/0004284.Bibcode:2000PASP..112..833H.doi:10.1086/316587.S2CID119361568.
  10. ^Richichi, A. (2000). "An Investigation of the multiple star Zet Cnc by a lunar occultation".Astronomy & Astrophysics.364:225–231.Bibcode:2000A&A...364..225R.
  11. ^Mason; Hartkopf, William I.; Wycoff, Gary L.; Holdenried, Ellis R. (2006)."Speckle Interferometry at the US Naval Observatory. XII".The Astronomical Journal.132(5): 2219–2230.Bibcode:2006AJ....132.2219M.doi:10.1086/508231.
  12. ^Fuhrmann, Klaus (February 2008), "Nearby stars of the Galactic disc and halo - IV",Monthly Notices of the Royal Astronomical Society,384(1): 173–224,Bibcode:2008MNRAS.384..173F,doi:10.1111/j.1365-2966.2007.12671.x
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