View source for Caelum

{{Short description|Constellation in the southern celestial hemisphere}}
{{For|the cargo ship|USS Caelum (AK-106)}}
{{Infobox constellation
| name = Caelum 
| abbreviation = Cae
| genitive = Caeli<ref name=tirionconst/>
| pronounce = {{IPAc-en|ˈ|s|iː|l|əm}}, genitive {{IPAc-en|ˈ|s|iː|l|aɪ}}
| symbolism = the [[chisel]]
| RA = {{RA|04|19.5}} to {{RA|05|05.1}}<ref name="boundary"/>
| dec= {{dec|−27.02}} to {{dec|−48.74}}<ref name="boundary"/>
| areatotal = 125
| arearank = 81st
| numbermainstars = 4
| numberbfstars = 8
| numberstarsplanets = 1
| numberbrightstars = 0
| numbernearbystars = 0
| brighteststarname = [[Alpha Caeli|α Cae]]
| starmagnitude = 4.45
| neareststarname = HD 30876
| stardistancely = 57.86
| stardistancepc = 17.75
| numbermessierobjects = 0
| meteorshowers = 1
| bordering = [[Columba (constellation)|Columba]]<br />[[Lepus (constellation)|Lepus]]<br />[[Eridanus (constellation)|Eridanus]]<br />[[Horologium (constellation)|Horologium]]<br />[[Dorado]]<br />[[Pictor]]
| latmax = [[40th parallel north|40]]
| latmin = [[South Pole|90]]
| month = January
| notes=}}
'''Caelum''' {{IPAc-en|ˈ|s|iː|l|əm}} is a faint [[constellation]] in the [[southern sky]], introduced in the 1750s by [[Nicolas Louis de Lacaille]] and counted among the [[88 modern constellations]]. Its name means "[[chisel]]" in [[Latin]], and it was formerly known as '''Caelum Sculptorium''' ("Engraver's Chisel"); it is a rare word, unrelated to the far more common Latin ''caelum'', meaning "[[sky]]", "[[heaven]]", or "[[atmosphere]]".<ref>Charlton T. Lewis, Ph.D. and. Charles Short, ''A Latin Dictionary'' Oxford University Press, 1879. Entries for ''caelum'' and ''caelum''.</ref> It is the eighth-smallest constellation, and subtends a [[solid angle]] of around 0.038&nbsp;[[steradian]]s, just less than that of [[Corona Australis]].

Due to its small size and location away from the plane of the [[Milky Way]], Caelum is a rather barren constellation, with few objects of interest. The constellation's brightest star, [[Alpha Caeli]], is only of [[apparent magnitude|magnitude]]&nbsp;4.45, and only one other star, [[Gamma1 Caeli|(Gamma) γ<sup>1</sup>&nbsp;Caeli]], is brighter than magnitude 5<sub>&nbsp;</sub>. Other notable objects in Caelum are [[RR Caeli|RR&nbsp;Caeli]], a [[binary star]] with one known planet approximately {{convert|20.13|pc|ly}} away; [[X Caeli|X&nbsp;Caeli]], a [[Delta Scuti variable]] that forms an [[Double star|optical double]] with γ<sup>1</sup>&nbsp;Caeli; and [[HE0450-2958]], a [[Seyfert galaxy]] that at first appeared as just a [[astrophysical jet|jet]], with no host galaxy visible.

== History ==
Caelum was incepted as one of fourteen southern constellations in the 18th century by [[Nicolas Louis de Lacaille]], a French astronomer and celebrated of the [[Age of Enlightenment]].<ref name="LacailleStarTales">{{cite web|url = http://www.ianridpath.com/startales/lacaille.html |work = Star Tales |title = Lacaille |last = Ridpath |first = Ian |access-date=3 May 2014 |publisher=self-published}}</ref>
It retains its name ''Burin'' among French speakers, Latinized in his catalogue of 1763 as ''Caelum Sculptoris'' (“''Engraver's Chisel''”).<ref>''Coelum australe stelliferum'', [[Nicolas Louis de Lacaille|N. L. de Lacaille]], 1763</ref>
[[File:Sidney Hall - Urania's Mirror - Canis Major, Lepus, Columba Noachi & Cela Sculptoris.jpg|thumb|left|Seen as “Cela Sculptoris” in the lower right of this 1825 star chart from ''[[Urania's Mirror]]''|alt=Caelum depicted in ''Urania's Mirror'']]
[[Francis Baily]] shortened this name to ''Caelum'', as suggested by [[John Herschel]].<ref name="CaelumStarTales">{{cite web |url = http://www.ianridpath.com/startales/caelum.html |work = Star Tales |title = Caelum |last = Ridpath |first = Ian |access-date=3 May 2014 |publisher=self-published}}</ref> In Lacaille's original chart, it was shown as a pair of engraver's tools: a standard [[Burin (engraving)|burin]] and more specific shape-forming [[échoppe]] tied by a ribbon, but came to be ascribed a simple chisel.<ref name="CaelumStarTales"/> [[Johann Elert Bode]] stated the name as plural with a singular possessor, ''Caela Scalptoris'' &ndash; in German (''die''<sub>&nbsp;</sub>) ''Grabstichel'' (“''the Engraver’s Chisels''”) &ndash; but this did not stick.<ref name="wagman"/><ref>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</ref>

{{clear|left}}

== Characteristics ==
Caelum is bordered by [[Dorado]] and [[Pictor]] to the south, [[Horologium (constellation)|Horologium]] and [[Eridanus (constellation)|Eridanus]] to the east, [[Lepus (constellation)|Lepus]] to the north, and [[Columba (constellation)|Columba]] to the west. Covering only 125&nbsp;[[square degree]]s, it ranks 81st of the [[88 modern constellations]] in size.

Its main [[asterism (astronomy)|asterism]] consists of four stars, and twenty stars in total are brighter than magnitude&nbsp;6.5<sub>&nbsp;</sub>.<ref name=tirionconst/>

The constellation's boundaries, as set by Belgian astronomer [[Eugène Joseph Delporte|Eugène Delporte]] in 1930, are a 12-sided polygon. In the [[equatorial coordinate system]], the [[right ascension]] coordinates of these borders lie between {{RA|04|19.5}} and {{RA|05|05.1}} and [[declination]]s of {{dec|−27.02}} to {{dec|−48.74}}.<ref name="boundary">{{cite journal | title=Caelum, Constellation Boundary | journal=The Constellations | publisher=International Astronomical Union | url=https://www.iau.org/public/themes/constellations/#cae|access-date=14 January 2014}}</ref> The [[International Astronomical Union]] (IAU) adopted the three-letter abbreviation “Cae” for the constellation in 1922.<ref name="pa30_469">{{cite journal | last=Russell | first=H. N.| title=The New International Symbols for the Constellations | journal=[[Popular Astronomy (US magazine)|Popular Astronomy]] | volume=30 |pages=469–71 |bibcode=1922PA.....30..469R | year=1922}}</ref>

Its main stars are visible in favourable conditions and with a clear southern horizon, for part of the year as far as about the [[41st parallel north]]<ref name=tirionconst>{{cite web| url=http://www.ianridpath.com/constellations1.html | title=Constellations: Andromeda–Indus | work= Star Tales |last=Ridpath |first=Ian |author-link=Ian Ridpath |publisher=self-published | access-date= 1 April 2014}}</ref>{{efn|1=While parts technically reach the horizon to observers between 41°N and [[62nd parallel north|62°N]], stars within a few degrees of the horizon are to all intents and purposes unobservable.<ref name=tirionconst/>}}

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 the [[Milky Way]].

== Notable features ==

=== Stars ===
{{See also|List of stars in Caelum}}
Caelum is a faint constellation: It has no star brighter than [[apparent magnitude|magnitude]]&nbsp;4 and only two stars brighter than magnitude&nbsp;5.

Lacaille gave six stars [[Bayer designations]], labeling them Alpha (α<sub>&nbsp;</sub>) to Zeta (ζ<sub>&nbsp;</sub>) in 1756, but omitted Epsilon (ε<sub>&nbsp;</sub>) and designated two adjacent stars as Gamma (γ<sub>&nbsp;</sub>). [[Johann Elert Bode|Bode]] extended the designations to Rho (ρ<sub>&nbsp;</sub>) for other stars, but most of these have fallen out of use.<ref name="wagman">{{cite book  | last = Wagman  | first = Morton  | year = 2003  | title = Lost Stars: Lost, Missing, and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others | publisher = The McDonald & Woodward Publishing Company | location = [[Blacksburg, Virginia|Blacksburg, VA]]  | isbn = 978-0-939923-78-6 |pages=58–59}}</ref> Caelum is too far south for any of its stars to bear [[Flamsteed designation]]s.{{efn|1=Southern constellations such as Caelum have no Flamsteed designations because Flamsteed only catalogued stars that were visible from England,.<ref name="Starnames">{{cite web |last1=Kaler |first1=J. B. |title=Star Names |publisher=[[University of Illinois at Urbana–Champaign]] |access-date=11 May 2014 |url=http://stars.astro.illinois.edu/sow/starname.html}}</ref>|date=14 February 2014}}

[[Image:Constellation Caelum.jpg|thumb|left|300px|The constellation Caelum as it can be seen by the [[naked eye]].|alt=Image of the constellation Caelum, showing the pattern of its stars as seen in the night sky]]
The brightest star, [[Alpha Caeli|(Alpha) α&nbsp;Caeli]], is a [[double star]], containing an [[F-type main-sequence star]] of magnitude&nbsp;4.45 and a [[red dwarf]] of magnitude&nbsp;12.5<sub>&nbsp;</sub>, {{convert|20.17|pc|ly}} from Earth.<ref name="AlphaSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=alf+Cae |title = * Alpha Caeli – Star in double system|publisher = [[SIMBAD]] | access-date = 13 January 2013}}</ref><ref name="Alpha2Simbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=CCDM%20J04406-4152%20B |title = GJ 174.1 B – Flare star|publisher = [[SIMBAD]] | access-date = 13 January 2013}}</ref> [[Beta Caeli|(Beta) β&nbsp;Caeli]], another [[F-type main-sequence star|F-type star]] of magnitude&nbsp;5.05<sub>&nbsp;</sub>, is further away, being located {{convert|28.67|pc|ly}} from Earth. Unlike α, β&nbsp;Caeli is a [[subgiant]] star, slightly evolved from the main sequence.<ref name="BetaSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=bet+Cae |title = LTT 2063 – High proper-motion Star|publisher = [[SIMBAD]] | access-date = 13 January 2013}}</ref> [[Delta Caeli|(Delta) δ&nbsp;Caeli]], also of magnitude&nbsp;5.05<sub>&nbsp;</sub>, is a [[B-type star|B-type]] subgiant and is much farther from Earth, at {{convert|216|pc|ly}}.<ref name="DeltaSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=del+Cae |title = * Delta Caeli – Star|publisher = [[SIMBAD]] | access-date = 13 January 2013}}</ref>

[[Gamma1 Caeli|(Gamma) γ<sup>1</sup>Caeli]] is a [[double star|double-star]] with a [[red giant]] primary of magnitude&nbsp;4.58 and a secondary of magnitude&nbsp;8.1<sub>&nbsp;</sub>. The primary is {{convert|55.59|pc|ly}} from Earth. The two components are difficult to resolve with small amateur telescopes because of their difference in [[visual magnitude]] and their close separation.<ref name="GammaSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=gam+Cae |title = * Gamma Caeli – Star|publisher = [[SIMBAD]] | access-date = 13 January 2013}}</ref> This star system forms an optical double with the unrelated [[X Caeli|X&nbsp;Caeli]] (previously named γ<sup>2</sup>Caeli), a [[Delta Scuti variable]] located {{convert|98.33|pc|ly}} from Earth.<ref name="XSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=X+Cae |title = V* X Caeli – Variable Star of Delta Scuti type|publisher = [[SIMBAD]] | access-date = 13 January 2013}}</ref> These are a class of short-period (six hours at most) pulsating stars that have been used as [[Cosmic distance ladder#Standard candles|standard candles]] and as subjects to study [[astroseismology]].<ref>{{cite web|url=http://www.aavso.org/vsots_delsct|title=Delta Scuti and the Delta Scuti Variables|last=Templeton|first=M. |date=16 July 2010|work=AAVSO Website|publisher=[[American Association of Variable Star Observers]]|access-date=2 February 2014}}</ref> The only other variable star in Caelum visible to the naked eye is [[RV Caeli|RV&nbsp;Caeli]], a [[pulsating variable|pulsating]] red giant of spectral type M1III,<ref name="RVSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=RV+Cae |title = V* RV Caeli – Pulsating variable Star |publisher = [[SIMBAD]] | access-date = 17 January 2013}}</ref> which varies between magnitudes&nbsp;6.44 and 6.56<sub>&nbsp;</sub>.<ref name=AAVSORV>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=4525 |title=RV Caeli |last1=X. |first1=V. S. |date=25 August 2009|work=AAVSO Website|publisher=American Association of Variable Star Observers|access-date=3 February 2014}}</ref>

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 Caeli|(Nu) ν&nbsp;Caeli]]<ref name="NuAstrostudio">{{cite web|author=Ashland Astronomy Studio: Where Art and Science Converge|title=Nu Caeli (HIP 22488)|url=http://www.astrostudio.org/xhip.php?hip=22488|access-date=15 January 2014|url-status=dead|archive-url=https://web.archive.org/web/20140129110728/http://www.astrostudio.org/xhip.php?hip=22488|archive-date=29 January 2014}}</ref> is another double star, containing a [[white giant]] of magnitude&nbsp;6.07<ref name="NuSimbad">{{cite news |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+30985 |title = HR 1557 – Star in double system |publisher = [[SIMBAD]] | access-date = 15 January 2013}}</ref> and a star of magnitude&nbsp;10.66, with unknown spectral type.<ref name="Nu2Simbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=CD-41%20%201593B |title = CD-41 1593B – Star in double system |publisher = [[SIMBAD]] | access-date = 15 January 2013}}</ref> The system is approximately {{convert|52.55|pc|ly}} away.<ref name="NuSimbad"/> [[Lambda Caeli|(Lambda) λ&nbsp;Caeli]],<ref name="LambdaAstrostudio">{{cite web|author=Ashland Astronomy Studio: Where Art and Science Converge|title=Lambda Caeli (HIP 21998)|url=http://www.astrostudio.org/xhip.php?hip=21998|access-date=15 January 2014|url-status=dead|archive-url=https://web.archive.org/web/20140129110726/http://www.astrostudio.org/xhip.php?hip=21998|archive-date=29 January 2014}}</ref> at magnitude&nbsp;6.24, is much redder and farther away, being a red giant around {{convert|227|pc|ly}} from Earth.<ref name="LambdaSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HR+1518 |title = HR 1518 – Star |publisher = [[SIMBAD]] | access-date = 15 January 2013}}</ref> [[Zeta Caeli|(Zeta) ζ&nbsp;Caeli]] is even fainter, being only of magnitude&nbsp;6.36<sub>&nbsp;</sub>. This star, located {{convert|132|pc|ly}} away, is a [[K-type star|K-type]] [[subgiant]] of spectral type K1.<ref name="ZetaSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=zet+Cae |title = Zeta Caeli – Star |publisher = [[SIMBAD]] | access-date = 15 January 2013}}</ref> The other twelve naked-eye stars in Caelum are not referred to by Bode's Bayer designations anymore, including RV&nbsp;Caeli.

[[File:Quasar HE0450-2958.jpg|thumb|right|The [[Seyfert galaxy]] [[HE0450-2958]], an unusual [[active galaxy]] in Caelum|alt=An image of the Seyfert galaxy HE0450-2958, showing the active nucleus]]

One of the nearest stars in Caelum is the [[eclipsing binary]] star [[RR Caeli|RR&nbsp;Caeli]], at a distance of {{convert|20.13|pc|ly}}.<ref name="RRSimbad"/> This star system consists of a dim [[red dwarf]] and a [[white dwarf]].<ref name="Bruch">{{Cite journal | last1 = Bruch | first1 = A. | last2 = Diaz | first2 = M. P. | doi = 10.1086/300471 | title = The Eclipsing Precataclysmic Binary RR Caeli | journal = The Astronomical Journal | volume = 116 | issue = 2 | pages = 908 | year = 1998 |bibcode = 1998AJ....116..908B | doi-access = free }}</ref> Despite its closeness to the Earth, the system's apparent magnitude is only 14.40<ref name="RRSimbad">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=RR+Cae |title = V* RR Caeli – Eclipsing binary of Algol type (detached) |publisher = [[SIMBAD]] | access-date = 15 January 2013}}</ref> due to the faintness of its components, and thus it cannot be easily seen with amateur equipment. The system is a [[Post common envelope binary|post-common-envelope binary]] and is losing [[angular momentum]] over time, which will eventually cause [[mass transfer]] from the red dwarf to the white dwarf. In approximately 9–20 billion years, this will cause the system to become a [[cataclysmic variable]].<ref name="Maxted">{{Cite journal | last1 = Maxted | first1 = P. F. L. | last2 = O'Donoghue | first2 = D. | last3 = Morales-Rueda | first3 = L. | last4 = Napiwotzki | first4 = R. | last5 = Smalley | first5 = B. | title = The mass and radius of the M-dwarf in the short-period eclipsing binary RR Caeli | doi = 10.1111/j.1365-2966.2007.11564.x| bibcode= 2007MNRAS.376..919M | arxiv = astro-ph/0702005| journal = Monthly Notices of the Royal Astronomical Society | volume = 376 | issue = 2 | pages = 919–928| year = 2007 | doi-access = free | s2cid = 3569936 }}</ref> In 2012, the system was found to contain a [[giant planet]], and there is evidence for a second substellar body.<ref name="Qian">{{Cite journal | last1 = Qian | first1 = S. B. | last2 = Liu | first2 = L. | last3 = Zhu | first3 = L. Y. | last4 = Dai | first4 = Z. B. | last5 = Fernández Lajús | first5 = E. | last6 = Baume | first6 = G. L. | doi = 10.1111/j.1745-3933.2012.01228.x | title = A circumbinary planet in orbit around the short-period white dwarf eclipsing binary RR Cae | journal = Monthly Notices of the Royal Astronomical Society: Letters | volume = 422 | issue = 1 | pages = L24–L27 | year = 2012 |arxiv = 1201.4205 |bibcode = 2012MNRAS.422L..24Q | s2cid = 119190656 }}</ref> {{As of|2021}}, it is believed two planets orbit RR Caeli.<ref name=Rattanamala2021>{{cite journal|last1=Rattanamala|first1=R.|last2=Awiphan|first2=S.|last3=Komonjinda|first3=S.|last4=Phriksee|first4=A.|last5=Sappankum|first5=P.|last6=A-thano|first6=N.|last7=Chitchak|first7=S.|last8=Rittipruk|first8=P.|last9=Sawangwit|first9=U.|last10=Poshyachinda|first10=S.|last11=Reichart|first11=D. E.|last12=Haislip|first12=J. B.|title=Eclipse timing variations in the WD+dM eclipsing binary RR Cae|arxiv=2109.09397|doi=10.1093/mnras/stad1733|year=2021|journal=[[Monthly Notices of the Royal Astronomical Society]]|issue=4|volume=523|pages=5086–5108|doi-access=free }}</ref>

Another nearby star is [[LHS 1678]], an [[astrometric binary]] located some 65&nbsp;[[light-year]]s away. The primary star is a [[red dwarf]] hosting three close-in exoplanets, all smaller than Earth, the secondary component is a likely [[brown dwarf]].<ref name=silverstein_2024>{{Cite journal |last1=Silverstein |first1=Michele L. |last2=Barclay |first2=Thomas |last3=Schlieder |first3=Joshua E. |last4=Collins |first4=Karen A. |last5=Schwarz |first5=Richard P. |last6=Hord |first6=Benjamin J. |last7=Rowe |first7=Jason F. |last8=Kruse |first8=Ethan |last9=Astudillo-Defru |first9=Nicola |last10=Bonfils |first10=Xavier |last11=Caldwell |first11=Douglas A. |last12=Charbonneau |first12=David |last13=Cloutier |first13=Ryan |last14=Collins |first14=Kevin I. |last15=Daylan |first15=Tansu |date=2024-03-01 |title=Validation of a Third Planet in the LHS 1678 System |journal=The Astronomical Journal |volume=167 |issue=6 |pages=255 |doi=10.3847/1538-3881/ad3040 |doi-access=free |arxiv=2403.00110 |bibcode=2024AJ....167..255S |issn=0004-6256}}</ref> This system is notable as the closest star to Alpha Caeli, just 3.3&nbsp;light-years distant.<ref>{{Cite web |title=★ LHS 1678 |url=https://www.stellarcatalog.com/stars/lhs-1678-a |access-date=2024-03-09 |website=Stellar Catalog |language=en}}</ref> Due to its closeness, α&nbsp;Caeli would shine at magnitude {{Val|-2.01}} from LHS&nbsp;1678,<ref>{{Cite web |title=★ Alpha Caeli |url=https://www.stellarcatalog.com/stars/alpha-caeli-a |access-date=2024-03-09 |website=Stellar Catalog |language=en}}</ref>{{efn|1=Using Alpha Caeli's [[absolute magnitude]] ({{val|-3.03}}) and distance from LHS 1678 (3.4 ly), its apparent magnitude can be calculated.<br />M<sub>abs</sub>&minus;5+5{{•}}log(distance (ly) / 3.26) = M<sub>app</sub>.}} brighter than [[Sirius]] in our sky.

=== Deep-sky objects ===
Due to its small size and location away from the plane of the [[Milky Way]], Caelum is rather devoid of deep-sky objects, and contains no [[Messier object]]s. The only [[deep-sky object]] in Caelum to receive much attention is [[HE0450-2958]], an unusual [[Seyfert galaxy]]. Originally, the jet's host galaxy proved elusive to find, and this jet appeared to be emanating from nothing.<ref name="Magain">{{Cite journal | last1 = Magain | first1 = P. | last2 = Letawe | first2 = G. R. | last3 = Courbin | first3 = F. D. R. | last4 = Jablonka | first4 = P. | last5 = Jahnke | first5 = K. | last6 = Meylan | first6 = G. | last7 = Wisotzki | first7 = L. | doi = 10.1038/nature04013 | title = Discovery of a bright quasar without a massive host galaxy | journal = Nature | volume = 437 | issue = 7057 | pages = 381–384 | year = 2005 | pmid =  16163349|arxiv = astro-ph/0509433 |bibcode = 2005Natur.437..381M | s2cid = 4303895 }}</ref> Although it has been suggested that the object is an ejected [[supermassive black hole]],<ref name="Hahenelt">{{Cite journal | last1 = Haehnelt | first1 = M. G. | last2 = Davies | first2 = M. B. | last3 = Rees | first3 = M. J. | title = Possible evidence for the ejection of a supermassive black hole from an ongoing merger of galaxies | doi = 10.1111/j.1745-3933.2005.00124.x | journal = Monthly Notices of the Royal Astronomical Society: Letters | volume = 366 | issue = 1 | pages = L22–L25 | year = 2006 | doi-access = free |arxiv = astro-ph/0511245 |bibcode = 2006MNRAS.366L..22H | s2cid = 18433710 }}</ref> the host is now agreed to be a small galaxy that is difficult to see due to light from the jet and a nearby [[starburst galaxy]].<ref name="Feain">{{Cite journal | last1 = Feain | first1 = I. J. | last2 = Papadopoulos | first2 = P. P. | last3 = Ekers | first3 = R. D. | last4 = Middelberg | first4 = E. | title = Dressing a Naked Quasar: Star Formation and Active Galactic Nucleus Feedback in HE 0450−2958 | doi = 10.1086/518027 | journal = The Astrophysical Journal | volume = 662 | issue = 2 | pages = 872 | year = 2007 |arxiv = astro-ph/0703101 |bibcode = 2007ApJ...662..872F | s2cid = 15556375 }}</ref>

The 13th magnitude [[planetary nebula]] PN 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, being {{val|20000|14000}} light-years below the Milky Way's 1000 light-year-thick disk.<ref>{{Cite Gaia DR2}}</ref>

Galaxies [[NGC 1595]], [[NGC 1598]], and the [[Carafe galaxy]] are known as the Carafe group. The Carafe galaxy is a Seyfert galaxy with ring. Its location is 4:28 / -47°54' (2000.0).<ref>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.</ref><ref>Hugh C. Maddocks, Deep-Sky Name Index 2000.0 (Foxon-Maddocks Associates, 1991).</ref>

==Notes==
{{Notelist}}

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== References ==
{{Reflist}}

== External links ==
{{Commons}}
* [http://www.starrynightphotos.com/constellations/fornax_phoenix.htm Starry Night Photography&nbsp;– Caelum Constellation]

{{Stars of Caelum}}
{{Constellations}}
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[[Category:Southern constellations]]
[[Category:Constellations listed by Lacaille]]