Editing Ara (constellation) (section)

== Features ==
[[Image:Constellation Ara.jpg|thumb|left|200px|The constellation Ara as it can be seen by the naked eye.]]

=== Stars ===
{{See also|List of stars in Ara}}
Bayer gave eight stars [[Bayer designation]]s, labelling them Alpha through to Theta, though he had never seen the constellation directly as it never rises above the horizon in Germany. After charting the southern constellations, French astronomer [[Nicolas-Louis de Lacaille]] recharted the stars of Ara from Alpha through to Sigma, including three pairs of stars next to each other as Epsilon, Kappa and Nu.{{sfn|Wagman|2003|pp=42–43}}

Ara contains part of the Milky Way to the south of Scorpius and thus has rich star fields.{{sfn|Ridpath|Tirion|2001|pp=82–83}} Within the constellation's borders, there are 71 stars brighter than or equal to [[apparent magnitude]]&nbsp;6.5.{{efn|1=Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.<ref>{{cite web|url=http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y|title=The Bortle Dark-Sky Scale|last=Bortle|first=John E.|date=February 2001|work=[[Sky & Telescope]]|access-date=26 August 2015}}</ref>}}<ref name=tirionconst/>

[[Beta Arae]], apparent magnitude 2.85, is the brightest star in the constellation, about 0.1 mag brighter than [[Alpha Arae]] although the difference in brightness between the two is undetectable by the unaided eye.<ref>{{cite web | first1=James B. | last1=Kaler | work=Stars | title=BETA ARA (Beta Arae) | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/betaara.html | access-date=17 September 2016}}</ref> Beta is an orange-hued star of [[spectral type]] K3Ib-IIa that has been classified as a [[supergiant]] or [[bright giant]],<ref name=aaa395_97>{{cite journal | last1=De Medeiros | first1=J. R. | last2=Udry | first2=S. | last3=Burki | first3=G. | last4=Mayor | first4=M. | title=A catalog of rotational and radial velocities for evolved stars. II. Ib supergiant stars | journal=Astronomy and Astrophysics | volume=395 | pages=97–98 |date=November 2002 | doi=10.1051/0004-6361:20021214 | bibcode=2002A&A...395...97D | url=http://www.aanda.org/articles/aa/pdf/2002/43/aa2890.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.aanda.org/articles/aa/pdf/2002/43/aa2890.pdf |archive-date=2022-10-09 |url-status=live | doi-access=free }}</ref> and lies around 650 light-years from Earth.<ref name=aaa474_2_653/> It is over 8 times as massive and 5,636 times as luminous as the Sun.<ref name=gaia>{{cite journal|bibcode=2015A&A...582A..49H|arxiv=1506.06095|title=Gaia FGK benchmark stars: Effective temperatures and surface gravities|journal=Astronomy & Astrophysics|volume=582|pages=A49|last1=Heiter|first1=U.|last2=Jofré|first2=P.|last3=Gustafsson|first3=B.|last4=Korn|first4=A. J.|last5=Soubiran|first5=C.|last6=Thévenin|first6=F.|year=2015|doi=10.1051/0004-6361/201526319|s2cid=53391939}}</ref> Close to Beta Arae is [[Gamma Arae]], a blue-hued supergiant of spectral type B1Ib. Of apparent magnitude 3.3, it is 1110 ± 60  light-years from Earth.<ref name=aaa474_2_653/> It has been estimated to be between 12.5 and 25 times as massive as the Sun,<ref name=mnras410_1_190>{{cite journal | last1=Tetzlaff | first1=N. | last2=Neuhäuser | first2=R. | last3=Hohle | first3=M. M. | title=A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun | journal=Monthly Notices of the Royal Astronomical Society | volume=410 | issue=1 | pages=190–200 |date=2011 | doi=10.1111/j.1365-2966.2010.17434.x | doi-access=free | bibcode=2011MNRAS.410..190T |arxiv = 1007.4883 | s2cid=118629873 }}</ref><ref name=aaa463_3_1093>{{cite journal | last1=Lefever | first1=K. | last2=Puls | first2=J. | last3=Aerts | first3=C. | title=Statistical properties of a sample of periodically variable B-type supergiants. Evidence for opacity-driven gravity-mode oscillations | journal=Astronomy and Astrophysics | volume=463 | issue=3 | pages=1093–1109 |date=March 2007 | doi=10.1051/0004-6361:20066038 | bibcode=2007A&A...463.1093L |arxiv = astro-ph/0611484 | s2cid=8783008 }}</ref> and have around 120,000 times its luminosity.<ref name=aaa463_3_1093/>

Alpha Arae is a [[B-type main sequence star|blue-white main sequence star]] of magnitude 2.95, that is 270 ± 20 light-years from Earth.<ref name=aaa474_2_653>{{cite journal | title=Validation of the new Hipparcos reduction | last=van Leeuwen | first=F. | journal=Astronomy and Astrophysics | volume=474 | issue=2 |date=November 2007 | pages=653–64 | doi=10.1051/0004-6361:20078357 | bibcode=2007A&A...474..653V |arxiv = 0708.1752 | s2cid=18759600 }}</ref> This star is around 9.6 times as massive as the Sun,<ref name=m07 /> and has an average of 4.5 times its radius.<ref name=aaa505_2_687>{{cite journal | last1=Meilland | first1=A. | last2=Stee | first2=Ph. | last3=Chesneau | first3=O. | last4=Jones | first4=C. | title=VLTI/MIDI observations of 7 classical Be stars | journal=Astronomy and Astrophysics | volume=505 | issue=2 | pages=687–93 |date=2009 | doi=10.1051/0004-6361/200911960 | bibcode=2009A&A...505..687M |arxiv = 0908.1239 | s2cid=12694072 }}</ref> It is  5,800 times as luminous as the Sun,<ref name=m07>{{cite journal | title=First direct detection of a Keplerian rotating disk around the Be star α Arae using AMBER/VLTI | first1=A. | last1=Meilland | journal=Astronomy and Astrophysics | volume=464 | issue=1 |date=March 2007 | pages=59–71 | doi=10.1051/0004-6361:20064848 | bibcode=2007A&A...464...59M |arxiv = astro-ph/0606404 | s2cid=55225830 |display-authors=etal| url=https://hal.archives-ouvertes.fr/hal-00078768 }}. See Tables 1 and 4 for parameters of the star, circumstellar disk, and polar winds.</ref> its energy emitted from its [[stellar atmosphere|outer envelope]] at an [[effective temperature]] of 18,044&nbsp;K.<ref name=aaa505_2_687/> A [[Be star]], Alpha Arae is surrounded by a dense equatorial disk of material in Keplerian (rather than uniform) rotation.  The star is losing mass by a polar [[stellar wind]] with a terminal velocity of approximately 1,000&nbsp;km/s.<ref name=m07/><ref>{{cite journal | title=First VLTI/MIDI observations of a Be star: Alpha Arae |author1=Chesneau, O. |author2=Meilland, A. |author3=Rivinius, T. |author4=Stee, Ph. |author5=Jankov, S. |author6=Domiciano de Souza, A. |author7=Graser, U. |author8=Herbst, T. |author9=Janot-Pacheco, E. |author10=Koehler, R. |author11=Leinert, C. |author12=Morel, S. |author13=Paresce, F. |author14=Richichi, A. |author15=Robbe-Dubois, S. |journal=Astronomy and Astrophysics|volume=435|issue=1 |year=2005| pages=275–287|doi=10.1051/0004-6361:20041954|bibcode=2005A&A...435..275C|arxiv = astro-ph/0501162 |s2cid=16747094 }}</ref>

The third brightest star in Ara at magnitude 3.13 is [[Zeta Arae]],<ref name=kalerzeta>{{cite web |last1=Kaler |first1=Jim |title=Zeta Arae |url=http://stars.astro.illinois.edu/sow/zetaara.html |website=Stars |publisher=University of Illinois |date=13 July 2012|access-date=12 September 2019}}</ref> an orange giant of spectral type K3III that is located 490 ± 10 light-years from Earth.<ref name=aaa474_2_653/> Around 7–8 times as massive as the Sun, it has swollen to a diameter around 114 times that of the Sun and is 3800 times as luminous.<ref name=cruzalebes>{{cite journal|bibcode=2013MNRAS.434..437C|arxiv=1306.3288|title=Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER|journal=Monthly Notices of the Royal Astronomical Society |volume=434|issue=1|pages=437|last1=Cruzalèbes|first1=P.|last2=Jorissen|first2=A.|last3=Rabbia|first3=Y.|last4=Sacuto|first4=S.|last5=Chiavassa|first5=A.|last6=Pasquato|first6=E.|last7=Plez|first7=B.|last8=Eriksson|first8=K.|last9=Spang|first9=A.|last10=Chesneau|first10=O.|year=2013|doi=10.1093/mnras/stt1037|doi-access=free |s2cid=49573767}}</ref> Were it not dimmer by intervening interstellar dust, it would be significantly brighter at magnitude 2.11.<ref name=kalerzeta/>

[[Delta Arae]] is a blue-white main sequence star of spectral type B8Vn and magnitude 3.6, 198 ± 4 light-years from Earth.<ref name=aaa474_2_653/> It is around 3.56 times as massive as the Sun.<ref name=apjss192_1_2>{{cite journal | last1=Shaya | first1=Ed J. | last2=Olling | first2=Rob P. | title=Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue | journal=The Astrophysical Journal Supplement | volume=192 | issue=1 | page=2 |date=January 2011 | doi=10.1088/0067-0049/192/1/2 | bibcode=2011ApJS..192....2S |arxiv = 1007.0425 | s2cid=119226823 }}</ref>

[[Epsilon1 Arae|Epsilon<sup>1</sup> Arae]] is an orange giant of apparent magnitude 4.1, 360 ± 10 light-years distant from Earth.<ref name=aaa474_2_653/> It is around 74% more massive than the Sun. At an age of about 1.7&nbsp;billion years, the [[stellar atmosphere|outer envelope]] of the star has expanded to almost 34 times the Sun's radius.<ref name=aaa458_2_609>{{cite journal | last1=da Silva | first1=L. | last2=Girardi | first2=L. | last3=Pasquini | first3=L. | last4=Setiawan | first4=J. | last5=von der Lühe | first5=O. | last6=de Medeiros | first6=J. R. | last7=Hatzes | first7=A. | last8=Döllinger | first8=M. P. | last9=Weiss | first9=A. | title=Basic physical parameters of a selected sample of evolved stars | journal=Astronomy and Astrophysics | volume=458 | issue=2 |date=November 2006 | pages=609–623 | doi=10.1051/0004-6361:20065105 | bibcode=2006A&A...458..609D |arxiv = astro-ph/0608160 | s2cid=9341088 }}</ref>

[[Eta Arae]] is an orange giant of apparent magnitude 3.76, located 299 ± 5 light-years distant from Earth.<ref name=aaa474_2_653/> Estimated to be around five billion years old, it has reached the [[giant star]] stage of its [[stellar evolution|evolution]]. With 1.12 times the [[mass of the Sun]], it has an [[stellar atmosphere|outer envelope]] that has expanded to 40 times the Sun's radius.<ref name=jofre2015>{{cite journal | title=Stellar parameters and chemical abundances of 223 evolved stars with and without planets | journal=Astronomy & Astrophysics | volume=574 | pages=A50 | year=2015 | last1=Jofré | first1=E. | last2=Petrucci | first2=R. | last3=Saffe | first3=C. | last4=Saker | first4=L. | last5=de la Villarmois | first5=E. Artur | last6=Chavero | first6=C. | last7=Gómez | first7=M. | last8=Mauas | first8=P. J. D. | bibcode=2015A&A...574A..50J | doi=10.1051/0004-6361/201424474 | arxiv=1410.6422 | s2cid=53666931 }}</ref> The star is now spinning so slowly that it takes more than eleven years to complete a single rotation.<ref name=aaa421_241>{{cite journal | last1=Setiawan | first1=J. | last2=Pasquini | first2=L. | last3=da Silva | first3=L. | last4=Hatzes | first4=A. P. | last5=von der Lühe | first5=O. | last6=Girardi | first6=L. | last7=de Medeiros | first7=J. R. | last8=Guenther | first8=E. | title=Precise radial velocity measurements of G and K giants. Multiple systems and variability trend along the Red Giant Branch | journal=Astronomy and Astrophysics | volume=421 | pages=241–254 |date=July 2004 | doi=10.1051/0004-6361:20041042-1 | bibcode=2004A&A...421..241S | doi-access=free }}</ref>

[[GX 339-4]] (V821 Arae) is a moderately strong variable galactic [[X-ray binary#Low-mass X-ray binary|low-mass X-ray binary]] (LMXB) source<ref>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=GX+339-4 SIMBAD]</ref><ref>Bradt, H.V.D., and McClintock, J.E., Annu. Rev. Astron. Astrophys., 21, 13-66 (1983)</ref> and [[black hole|black-hole]] candidate that flares from time to time. From spectroscopic measurements, the mass of the black-hole was found to be at least of 5.8 solar masses.<ref>{{Cite journal|title = Dynamical Evidence for a Black Hole in GX 339-4|author1=Hynes, R. I. |author2=Steeghs, D. |author3=Casares, J. |author4=Charles, P. A. |author5=O'Brien, K. |date = February 2003|journal = The Astrophysical Journal| volume = 583| issue = 2, pp. L95–L98|doi = 10.1086/368108|bibcode=2003ApJ...583L..95H |pages=L95–L98|arxiv = astro-ph/0301127 |s2cid=16820881 }}</ref>

[[Exoplanet]]s have been discovered in seven star systems in the constellation.<ref name=bagnall>{{Cite book|title=The Star Atlas Companion : What You Need to Know about the Constellations|last=Bagnall|first= Philip M. |date=2012|publisher=[[Springer Science+Business Media|Springer]] |pages= 50–54| location=New York | isbn=9781461408307|oclc=794225463}}</ref>  [[Mu Arae]] (Cervantes<ref name="IAU-LSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=30 July 2018}}</ref>) is a sunlike star that hosts four planets.<ref name="pepe">{{Cite journal|author=Pepe, F.|title=The HARPS search for southern extra-solar planets. IX. μ Ara, a system with four planets|journal=Astronomy and Astrophysics|volume=462|issue=2|pages=769–776|year=2006|arxiv=astro-ph/0608396|last2= Correia|first2=A. C. M.|last3= Mayor|first3=M.|last4= Tamuz|first4=O.|last5= Benz|first5=W.|last6= Bertaux|first6=J. -L.|last7= Bouchy|first7=F.|last8= Couetdic|first8=J.|last9= Laskar|first9=J.|last10= Lovis|first10=C.|last11= Naef|first11=D.|last12= Queloz|first12=D.|last13= Santos|first13=N. C.|last14= Sivan|first14=J. -P.|last15= Sosnowska|first15=D.|last16= Udry|first16=S.|doi=10.1051/0004-6361:20066194|bibcode = 2007A&A...462..769P |s2cid=119071803}}</ref> [[HD 152079]] is a sunlike star with a jupiter-like planet with an orbital period of 2097 ± 930 days.<ref name="Arriagada2010">{{cite journal | title=Five Long-period Extrasolar Planets in Eccentric orbits from the Magellan Planet Search Program | last1=Arriagada | first1=Pamela | last2=Butler | first2=R. Paul | last3=Minniti | first3=Dante | last4=López-Morales | first4=Mercedes | last5=Shectman | first5=Stephen A. | last6=Adams | first6=Fred C. | last7=Boss | first7=Alan P. | last8=Chambers | first8=John E. | display-authors=1 | journal=The Astrophysical Journal | volume=711 | issue=2 | pages=1229–35 | date=2010 | arxiv=1001.4093 | bibcode=2010ApJ...711.1229A | doi=10.1088/0004-637X/711/2/1229 | s2cid=118682009 }}</ref> [[HD 154672]] is an ageing sunlike star with a [[Hot Jupiter]]. [[HD 154857]] is a sunlike star with one confirmed and one suspected planet. [[HD 156411]] is a star hotter and larger than the sun with a gas giant planet in orbit. [[Gliese 674]] is a nearby red dwarf star with a planet. [[Gliese 676]] is a binary star system composed of two red dwarves with four planets.

=== Deep-sky objects ===
[[File:IC 4653 a Familiar Sight.jpg|thumb|[[IC 4653]] galaxy taken by Hubble.<ref>{{cite web |title=A Familiar Sight |url=https://www.spacetelescope.org/images/potw1942a/ |website=www.spacetelescope.org |access-date=23 October 2019 |language=en}}</ref>]]
The northwest corner of Ara is crossed by the [[galactic plane]] of the [[Milky Way]] and contains several [[open cluster]]s (notably [[NGC 6200]]) and [[diffuse nebula]]e (including the bright cluster/nebula pair [[NGC 6188]] and [[NGC 6193]]). The brightest of the [[globular cluster]]s, sixth magnitude [[NGC 6397]], lies at a distance of just {{convert|6500|ly|km}}, making it one of the closest globular clusters to the [[Solar System]].{{sfn|Dunlop|2005}}

Ara also contains [[Westerlund 1]], a [[super star cluster]] containing itself the possible [[Red supergiant star|red supergiant]] [[Westerlund 1-237]] and the [[red supergiant]] [[Westerlund 1-26]]. The latter is one of the [[List of largest stars|largest stars known]] with an estimate varying between {{solar radius|1,168|link=y}}<ref name=paulo2018>{{cite thesis |doi=10.11606/D.14.2019.tde-12092018-161841 |title=The Red Supergiants in the Supermassive Stellar Cluster Westerlund 1 |year=2019 |last1=Arévalo |first1=Aura |doi-access=free |lang=en |publisher=[[University of São Paulo]] |type=Master's thesis}}</ref> and {{solar radius|2,519|link=y}}.<ref name=thomas>{{Cite journal|arxiv=1209.6427|last1=Fok|first1=Thomas K. T.|title=Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters|journal=The Astrophysical Journal|volume=760|issue=1|pages=65|last2=Nakashima|first2=Jun-ichi|last3=Yung|first3=Bosco H. K.|last4=Hsia|first4=Chih-Hao|last5=Deguchi|first5=Shuji|year=2012|doi=10.1088/0004-637X/760/1/65|bibcode=2012ApJ...760...65F|s2cid=53393926}}</ref>

Although Ara lies close to the heart of the Milky Way, two [[spiral galaxies]] ([[NGC 6215]] and [[NGC 6221]]) are visible near star [[Eta Arae]].{{sfn|Dunlop|2005}}

==== Open clusters ====
* [[NGC 6193]] is an [[open cluster]] containing approximately 30 stars with an overall magnitude of 5.0 and a size of 0.25 square degrees, about half the size of the [[full Moon]]. It is approximately 4200 light-years from Earth. It has one bright member, a double star with a blue-white hued primary of magnitude 5.6 and a secondary of magnitude 6.9. NGC 6193 is surrounded by [[NGC 6188]], a faint [[nebula]] only normally visible in [[astrophotography|long-exposure photographs]].{{sfn|Ridpath|Tirion|2001|pp=82–83}}
* [[NGC 6200]]
* [[NGC 6204]]
* [[NGC 6208]]
* [[NGC 6250]]
* [[NGC 6253]]
* [[IC 4651]]

==== Globular clusters ====
* [[NGC 6352]]
* [[NGC 6362]]
* [[NGC 6397]] is a [[globular cluster]] with an overall magnitude of 6.0; it is visible to the naked eye under exceptionally dark skies and is normally visible in binoculars. It is a fairly close globular cluster, at a distance of 10,500 light-years.{{sfn|Ridpath|Tirion|2001|pp=82–83}}

=== Planetary Nebulae ===
* The [[Stingray Nebula]] (Hen 3–1357), the youngest known planetary nebula as of 2010, formed in Ara; the light from its formation was first observable around 1987.
* [[NGC 6326]].  A planetary nebula that might have a binary system at its center.