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Caelum

For the cargo ship, seeUSS Caelum (AK-106).

Caelum/ˈsiːləm/is a faintconstellationin thesouthern sky,introduced in the 1750s byNicolas Louis de Lacailleand counted among the88 modern constellations.Its name means "chisel"inLatin,and it was formerly known asCaelum Sculptorium( "Engraver's Chisel" ); it is a rare word, unrelated to the far more common Latincaelum,meaning "sky","heaven",or"atmosphere".[3]It is the eighth-smallest constellation, and subtends asolid angleof around 0.038steradians,just less than that ofCorona Australis.

Caelum
Constellation
Caelum
List of stars in Caelum
AbbreviationCae
GenitiveCaeli[1]
Pronunciation/ˈsiːləm/,genitive/ˈsiːlaɪ/
Symbolismthechisel
Right ascension04h19.5mto05h05.1m[2]
Declination−27.02° to −48.74°[2]
Area125 sq. deg. (81st)
Main stars4
Bayer/Flamsteed
stars		8
Stars withplanets1
Stars brighter than 3.00m0
Stars within 10.00 pc (32.62 ly)0
Brightest starα Cae(4.45m)
Messier objects0
Meteor showers1
Bordering
constellations		Columba
Lepus
Eridanus
Horologium
Dorado
Pictor
Visible at latitudes between +40° and −90°.
Best visible at 21:00 (9 p.m.) during the month ofJanuary.

Due to its small size and location away from the plane of theMilky Way,Caelum is a rather barren constellation, with few objects of interest. The constellation's brightest star,Alpha Caeli,is only ofmagnitude4.45, and only one other star,(Gamma) γ1Caeli,is brighter than magnitude 5.Other notable objects in Caelum areRR Caeli,abinary starwith one known planet approximately 20.13 parsecs (65.7 ly) away;X Caeli,aDelta Scuti variablethat forms anoptical doublewith γ1Caeli; andHE0450-2958,aSeyfert galaxythat at first appeared as just ajet,with no host galaxy visible.

History

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Caelum was incepted as one of fourteen southern constellations in the 18th century byNicolas Louis de Lacaille,a French astronomer and celebrated of theAge of Enlightenment.[4] It retains its nameBurinamong French speakers, latinized in his catalogue of 1763 asCaelum Sculptoris( “Engraver's Chisel”).[5]

Seen as “Cela Sculptoris” in the lower right of this 1825 star chart fromUrania's Mirror

Francis Bailyshortened this name toCaelum,as suggested byJohn Herschel.[6]In Lacaille's original chart, it was shown as a pair of engraver's tools: a standardburinand more specific shape-formingéchoppetied by a ribbon, but came to be ascribed a simple chisel.[6]Johann Elert Bodestated the name as plural with a singular possessor,Caela Scalptoris– in German (die)Grabstichel( “the Engraver’s Chisels”) – but this did not stick.[7][8]

Characteristics

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Caelum is bordered byDoradoandPictorto the south,HorologiumandEridanusto the east,Lepusto the north, andColumbato the west. Covering only 125square degrees,it ranks 81st of the88 modern constellationsin size.

Its mainasterismconsists of four stars, and twenty stars in total are brighter than magnitude 6.5.[1]

The constellation's boundaries, as set by Belgian astronomerEugène Delportein 1930, are a 12-sided polygon. In theequatorial coordinate system,theright ascensioncoordinates of these borders lie between04h19.5mand05h05.1manddeclinationsof −27.02° to −48.74°.[2]TheInternational Astronomical Union(IAU) adopted the three-letter abbreviation “Cae” for the constellation in 1922.[9]

Its main stars are visible in favourable conditions and with a clear southern horizon, for part of the year as far as about the41st parallel north[1][a]

These stars avoid being engulfed by daylight for some of every day (when above the horizon) to viewers in mid- and well-inhabited higher latitudes of the Southern Hemisphere. Caelum shares with (to the north) Taurus, Eridanus and Orion midnight culmination in December (high summer), resulting in this fact. In winter (such as June) the constellation can be observed sufficiently inset from the horizons during its rising before dawn and/or setting after dusk as it culminates then at around mid-day, well above the sun. In South Africa, Argentina, their sub-tropical neighbouring areas and some of Australia in high June the key stars may be traced before dawn in the east; near the equator the stars lose night potential in May to June; they ill-compete with the Sun in northern tropics and sub-tropics from late February to mid-September with March being unfavorable as to post-sunset due to the light of theMilky Way.

Notable features

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Stars

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See also:List of stars in Caelum

Caelum is a faint constellation: It has no star brighter thanmagnitude4 and only two stars brighter than magnitude 5.

Lacaille gave six starsBayer designations,labeling them Alpha (α) to Zeta (ζ) in 1756, but omitted Epsilon (ε) and designated two adjacent stars as Gamma (γ).Bodeextended the designations to Rho (ρ) for other stars, but most of these have fallen out of use.[7]Caelum is too far south for any of its stars to bearFlamsteed designations.[b]

The constellation Caelum as it can be seen by thenaked eye.

The brightest star,(Alpha) α Caeli,is adouble star,containing anF-type main-sequence starof magnitude 4.45 and ared dwarfof magnitude 12.5,20.17 parsecs (65.8 ly) from Earth.[11][12](Beta) β Caeli,anotherF-type starof magnitude 5.05,is further away, being located 28.67 parsecs (93.5 ly) from Earth. Unlike α, β Caeli is asubgiantstar, slightly evolved from the main sequence.[13](Delta) δ Caeli,also of magnitude 5.05,is aB-typesubgiant and is much farther from Earth, at 216 parsecs (700 ly).[14]

(Gamma) γ1Caeliis adouble-starwith ared giantprimary of magnitude 4.58 and a secondary of magnitude 8.1.The primary is 55.59 parsecs (181.3 ly) from Earth. The two components are difficult to resolve with small amateur telescopes because of their difference invisual magnitudeand their close separation.[15]This star system forms an optical double with the unrelatedX Caeli(previously named γ2Caeli), aDelta Scuti variablelocated 98.33 parsecs (320.7 ly) from Earth.[16]These are a class of short-period (six hours at most) pulsating stars that have been used asstandard candlesand as subjects to studyastroseismology.[17]The only other variable star in Caelum visible to the naked eye isRV Caeli,apulsatingred giant of spectral type M1III,[18]which varies between magnitudes 6.44 and 6.56.[19]

Three other stars in Caelum are still occasionally referred to by their Bayer designations, although they are only on the edge of naked-eye visibility.(Nu) ν Caeli[20]is another double star, containing awhite giantof magnitude 6.07[21]and a star of magnitude 10.66, with unknown spectral type.[22]The system is approximately 52.55 parsecs (171.4 ly) away.[21](Lambda) λ Caeli,[23]at magnitude 6.24, is much redder and farther away, being a red giant around 227 parsecs (740 ly) from Earth.[24](Zeta) ζ Caeliis even fainter, being only of magnitude 6.36.This star, located 132 parsecs (430 ly) away, is aK-typesubgiantof spectral type K1.[25]The other twelve naked-eye stars in Caelum are not referred to by Bode's Bayer designations anymore, including RV Caeli.

TheSeyfert galaxyHE0450-2958,an unusualactive galaxyin Caelum

One of the nearest stars in Caelum is theeclipsing binarystarRR Caeli,at a distance of 20.13 parsecs (65.7 ly).[26]This star system consists of a dimred dwarfand awhite dwarf.[27]Despite its closeness to the Earth, the system's apparent magnitude is only 14.40[26]due to the faintness of its components, and thus it cannot be easily seen with amateur equipment. The system is apost-common-envelope binaryand is losingangular momentumover time, which will eventually causemass transferfrom the red dwarf to the white dwarf. In approximately 9–20 billion years, this will cause the system to become acataclysmic variable.[28]In 2012, the system was found to contain agiant planet,and there is evidence for a second substellar body.[29]As of 2021,it is believed two planets orbit RR Caeli.[30]

Another nearby star isLHS 1678,anastrometric binarylocated some 65light-yearsaway. The primary star is ared dwarfhosting three close-in exoplanets, all smaller than Earth, the secondary component is a likelybrown dwarf.[31]This system is notable as the closest star to Alpha Caeli, just 3.3 light-years distant.[32]Due to its closeness, α Caeli would shine at magnitude−2.01from LHS 1678,[33][c]brighter thanSiriusin our sky.

Deep-sky objects

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Due to its small size and location away from the plane of theMilky Way,Caelum is rather devoid of deep-sky objects, and contains noMessier objects.The onlydeep-sky objectin Caelum to receive much attention isHE0450-2958,an unusualSeyfert galaxy.Originally, the jet's host galaxy proved elusive to find, and this jet appeared to be emanating from nothing.[34]Although it has been suggested that the object is an ejectedsupermassive black hole,[35]the host is now agreed to be a small galaxy that is difficult to see due to light from the jet and a nearbystarburst galaxy.[36]

The 13th magnitudeplanetary nebulaPN G243-37.1 is also in the eastern regions of the constellation. It is one of only a few planetary nebulae found in the galactic halo, being20000±14000light-years below the Milky Way's 1000 light-year-thick disk.[37]

GalaxiesNGC 1595,NGC 1598,and theCarafe galaxyare known as the Carafe group. The Carafe galaxy is a Seyfert galaxy with ring. Its location is 4:28 / -47°54' (2000.0).[38][39]

Notes

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  1. ^While parts technically reach the horizon to observers between 41°N and62°N,stars within a few degrees of the horizon are to all intents and purposes unobservable.[1]
  2. ^Southern constellations such as Caelum have no Flamsteed designations because Flamsteed only catalogued stars that were visible from England,.[10]
  3. ^Using Alpha Caeli'sabsolute magnitude(−3.03) and distance from LHS 1678 (3.4 ly), its apparent magnitude can be calculated.
    Mabs−5+5 • log(distance (ly) / 3.26) = Mapp.

References

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  1. ^abcdRidpath, Ian."Constellations: Andromeda–Indus".Star Tales.self-published.Retrieved1 April2014.
  2. ^abc"Caelum, Constellation Boundary".The Constellations.International Astronomical Union.Retrieved14 January2014.
  3. ^Charlton T. Lewis, Ph.D. and. Charles Short,A Latin DictionaryOxford University Press, 1879. Entries forcaelumandcaelum.
  4. ^Ridpath, Ian."Lacaille".Star Tales.self-published.Retrieved3 May2014.
  5. ^Coelum australe stelliferum,N. L. de Lacaille,1763
  6. ^abRidpath, Ian."Caelum".Star Tales.self-published.Retrieved3 May2014.
  7. ^abWagman, Morton (2003).Lost Stars: Lost, Missing, and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others.Blacksburg, VA:The McDonald & Woodward Publishing Company. pp.58–59.ISBN978-0-939923-78-6.
  8. ^J. E. Bode:Allgemeine Beschreibung und Nachweisung der Gestirne nebst Verzeichniß der geraden Aufsteigung und Abweichung von 17240 Sternen, Doppelsternen, Nebelflecken und Sternhaufen.Berlin, 1801, p.17
  9. ^Russell, H. N. (1922). "The New International Symbols for the Constellations".Popular Astronomy.30:469–71.Bibcode:1922PA.....30..469R.
  10. ^Kaler, J. B."Star Names".University of Illinois at Urbana–Champaign.Retrieved11 May2014.
  11. ^"* Alpha Caeli – Star in double system".SIMBAD.Retrieved13 January2013.
  12. ^"GJ 174.1 B – Flare star".SIMBAD.Retrieved13 January2013.
  13. ^"LTT 2063 – High proper-motion Star".SIMBAD.Retrieved13 January2013.
  14. ^"* Delta Caeli – Star".SIMBAD.Retrieved13 January2013.
  15. ^"* Gamma Caeli – Star".SIMBAD.Retrieved13 January2013.
  16. ^"V* X Caeli – Variable Star of Delta Scuti type".SIMBAD.Retrieved13 January2013.
  17. ^Templeton, M. (16 July 2010)."Delta Scuti and the Delta Scuti Variables".AAVSO Website.American Association of Variable Star Observers.Retrieved2 February2014.
  18. ^"V* RV Caeli – Pulsating variable Star".SIMBAD.Retrieved17 January2013.
  19. ^X., V. S. (25 August 2009)."RV Caeli".AAVSO Website.American Association of Variable Star Observers.Retrieved3 February2014.
  20. ^Ashland Astronomy Studio: Where Art and Science Converge."Nu Caeli (HIP 22488)".Archived fromthe originalon 29 January 2014.Retrieved15 January2014.
  21. ^ab"HR 1557 – Star in double system".SIMBAD.Retrieved15 January2013.
  22. ^"CD-41 1593B – Star in double system".SIMBAD.Retrieved15 January2013.
  23. ^Ashland Astronomy Studio: Where Art and Science Converge."Lambda Caeli (HIP 21998)".Archived fromthe originalon 29 January 2014.Retrieved15 January2014.
  24. ^"HR 1518 – Star".SIMBAD.Retrieved15 January2013.
  25. ^"Zeta Caeli – Star".SIMBAD.Retrieved15 January2013.
  26. ^ab"V* RR Caeli – Eclipsing binary of Algol type (detached)".SIMBAD.Retrieved15 January2013.
  27. ^Bruch, A.; Diaz, M. P. (1998)."The Eclipsing Precataclysmic Binary RR Caeli".The Astronomical Journal.116(2): 908.Bibcode:1998AJ....116..908B.doi:10.1086/300471.
  28. ^Maxted, P. F. L.; O'Donoghue, D.; Morales-Rueda, L.; Napiwotzki, R.; Smalley, B. (2007)."The mass and radius of the M-dwarf in the short-period eclipsing binary RR Caeli".Monthly Notices of the Royal Astronomical Society.376(2):919–928.arXiv:astro-ph/0702005.Bibcode:2007MNRAS.376..919M.doi:10.1111/j.1365-2966.2007.11564.x.S2CID3569936.
  29. ^Qian, S. B.; Liu, L.; Zhu, L. Y.; Dai, Z. B.; Fernández Lajús, E.; Baume, G. L. (2012). "A circumbinary planet in orbit around the short-period white dwarf eclipsing binary RR Cae".Monthly Notices of the Royal Astronomical Society: Letters.422(1):L24 –L27.arXiv:1201.4205.Bibcode:2012MNRAS.422L..24Q.doi:10.1111/j.1745-3933.2012.01228.x.S2CID119190656.
  30. ^Rattanamala, R.; Awiphan, S.; Komonjinda, S.; Phriksee, A.; Sappankum, P.; A-thano, N.; Chitchak, S.; Rittipruk, P.; Sawangwit, U.; Poshyachinda, S.; Reichart, D. E.; Haislip, J. B. (2021)."Eclipse timing variations in the WD+dM eclipsing binary RR Cae".Monthly Notices of the Royal Astronomical Society.523(4):5086–5108.arXiv:2109.09397.doi:10.1093/mnras/stad1733.
  31. ^Silverstein, Michele L.; Barclay, Thomas; Schlieder, Joshua E.; Collins, Karen A.; Schwarz, Richard P.; Hord, Benjamin J.; Rowe, Jason F.; Kruse, Ethan; Astudillo-Defru, Nicola; Bonfils, Xavier; Caldwell, Douglas A.; Charbonneau, David; Cloutier, Ryan; Collins, Kevin I.; Daylan, Tansu (2024-03-01)."Validation of a Third Planet in the LHS 1678 System".The Astronomical Journal.167(6): 255.arXiv:2403.00110.Bibcode:2024AJ....167..255S.doi:10.3847/1538-3881/ad3040.ISSN0004-6256.
  32. ^"★ LHS 1678".Stellar Catalog.Retrieved2024-03-09.
  33. ^"★ Alpha Caeli".Stellar Catalog.Retrieved2024-03-09.
  34. ^Magain, P.; Letawe, G. R.; Courbin, F. D. R.; Jablonka, P.; Jahnke, K.; Meylan, G.; Wisotzki, L. (2005). "Discovery of a bright quasar without a massive host galaxy".Nature.437(7057):381–384.arXiv:astro-ph/0509433.Bibcode:2005Natur.437..381M.doi:10.1038/nature04013.PMID16163349.S2CID4303895.
  35. ^Haehnelt, M. G.; Davies, M. B.; Rees, M. J. (2006)."Possible evidence for the ejection of a supermassive black hole from an ongoing merger of galaxies".Monthly Notices of the Royal Astronomical Society: Letters.366(1):L22 –L25.arXiv:astro-ph/0511245.Bibcode:2006MNRAS.366L..22H.doi:10.1111/j.1745-3933.2005.00124.x.S2CID18433710.
  36. ^Feain, I. J.; Papadopoulos, P. P.; Ekers, R. D.; Middelberg, E. (2007). "Dressing a Naked Quasar: Star Formation and Active Galactic Nucleus Feedback in HE 0450−2958".The Astrophysical Journal.662(2): 872.arXiv:astro-ph/0703101.Bibcode:2007ApJ...662..872F.doi:10.1086/518027.S2CID15556375.
  37. ^Brown, A. G. A.;et al. (Gaia collaboration) (August 2018)."GaiaData Release 2: Summary of the contents and survey properties ".Astronomy & Astrophysics.616.A1.arXiv:1804.09365.Bibcode:2018A&A...616A...1G.doi:10.1051/0004-6361/201833051.
  38. ^Sky Catalogue 2000.0, Volume 2: Double Stars, Variable Stars and Nonstellar Objects (edited by Alan Hirshfeld and Roger W. Sinnott, 1985). Chapter 3: Glossary of Selected Astronomical Names.
  39. ^Hugh C. Maddocks, Deep-Sky Name Index 2000.0 (Foxon-Maddocks Associates, 1991).
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