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Mu Arae

2021-03-14T19:48:28Z

JDuntemann: Created page with "{{Short description|Star in the constellation Ara}} {{Use dmy dates|date=October 2019}} {{Starbox begin | name = Mu Arae }} {{Starbox image | image = | caption = Mu Arae }} {{..."

{{Short description|Star in the constellation Ara}}
{{Use dmy dates|date=October 2019}}
{{Starbox begin
| name = Mu Arae
}}
{{Starbox image
| image =
| caption = Mu Arae
}}
{{Starbox observe
| epoch = J2000.0
| constell = [[Ara (constellation)|Ara]]
| ra = {{RA|17|44|08.70114}}<ref name=aaa474_2_653/>
| dec = {{DEC|−51|50|02.5853}}<ref name=aaa474_2_653/>
| appmag_v = +5.12
}}
{{Starbox character
| class = G3IV–V<ref name=aj132_1_161/>
| b-v = +0.70<ref name=ibsh8_30/>
| u-b = +0.24<ref name=ibsh8_30/>
| r-i = 0.2
| v-r =
| variable =
}}
{{Starbox astrometry
| radial_v = −9.0<ref name=scfs/>
| prop_mo_ra = −16.85<ref name=aaa474_2_653/>
| prop_mo_dec = −190.60<ref name=aaa474_2_653/>
| parallax = 64.47
| p_error = 0.31
| parallax_footnote =<ref name=aaa474_2_653/>
| absmag_v = +4.17<ref name=Anderson2012/>
| dist_ly =
| dist_pc =
}}
{{Starbox detail
| age_gyr = {{nowrap|6.34 ± 0.40}}<ref name="soriano2009">{{cite journal|title=New seismic analysis of the exoplanet-host star Mu Arae|arxiv=0903.5475 |year=2009 |last1=Soriano | first1=M. |last2=Vauclair |first2=S. |doi=10.1051/0004-6361/200911862 |volume=513 |journal=Astronomy and Astrophysics |page=A49 |bibcode=2010A&A...513A..49S}}</ref>
| metal = {{nowrap|200 ± 5%}}<ref name="soriano2009" /><ref group="note">From [Fe/H] = 0.30 ± 0.01</ref>
| metal_fe = {{nowrap|0.30 ± 0.01}}<ref name="soriano2009" />
| mass = {{nowrap|1.10 ± 0.01}}<ref name="soriano2009" />
| radius = {{nowrap|1.36 ± 0.01}}<ref name="soriano2009" />
| rotation = 31 days
| rotational_velocity = 1.4<ref name=mnras405_3_1907/>
| gravity = 4.19<ref name=aj132_1_161/>
| luminosity = {{nowrap|1.90 ± 0.10}}<ref name="soriano2009" />
| temperature = {{nowrap|5820 ± 40}}<ref name="soriano2009" />
}}
{{Starbox catalog
| names = Cervantes, [[Bonner Durchmusterung|CD]] −51° 11094, [[Fifth Fundamental Catalogue|FK5]] 662, [[Boss General Catalogue|GC]] 24024, [[Gliese–Jahreiß catalogue|GJ]] 691, [[Henry Draper Catalogue|HD]] 160691, [[Hipparcos catalogue|HIP]] 86796, [[Harvard Revised catalogue|HR]] 6585, [[Smithsonian Astrophysical Observatory catalogue|SAO]] 244981
}}
{{Starbox reference
| Simbad = LTT+7053
| ARICNS = 01434
| NSTED = Mu+Arae
| EPE = mu+Ara
}}
{{Starbox end}}
'''Mu Arae''' ('''μ Arae''', abbreviated '''Mu Ara''', '''μ Ara'''), often designated '''HD 160691''', officially named '''Cervantes''' {{IPAc-en|s|ɜːr|'|v|æ|n|t|iː|z}} {{respell|sur|VAN|teez}},<ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}</ref> is a [[main sequence]] [[G V star|G-type]] [[star]] approximately 50 [[light-year]]s away from the [[Sun]] in the [[constellation]] of [[Ara (constellation)|Ara]]. The star has a [[planetary system]] with four known [[Exoplanet|extrasolar planets]] (designated [[Mu Arae b]], [[Mu Arae c|c]], [[Mu Arae d|d]] and [[Mu Arae e|e]]; later named Quijote, Dulcinea, Rocinante and Sancho, respectively), three of them with masses comparable with that of [[Jupiter]]. Mu Arae c, the innermost, was the first [[hot Neptune]] or [[super-Earth]] discovered.

== Nomenclature ==

''μ Arae'' ([[Latinisation of names|Latinised]] to ''Mu Arae'') is the star's [[Bayer designation]]. HD 160691 is the entry in the [[Henry Draper Catalogue]].

The established convention for extrasolar planets is that the planets receive designations consisting of the star's name followed by lower-case [[Latin alphabet|Roman letters]] starting from "b", in order of discovery.<ref name="planetnaming">{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |year=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U.}}</ref> This system was used by a team led by [[Krzysztof Goździewski]].<ref name="gozdziewski"/> On the other hand, a team led by [[Francesco Pepe]] proposed a modification of the designation system, where the planets are designated in order of characterization.<ref name="pepe"/> Since the parameters of the outermost planet were poorly constrained before the introduction of the 4-planet model of the system, this results in a different order of designations for the planets in the Mu Arae system. Both systems agree on the designation of the 640-day planet as "b". The old system designates the 9-day planet as "d", the 310-day planet as "e" and the outer planet as "c". Since the [[International Astronomical Union]] has not defined an official system for designations of extrasolar planets,<ref>{{cite web|url=http://www.iau.org/PLANETS_AROUND_OTHER_STARS.247.0.html|title=Planets Around Other Stars|publisher=IAU|access-date=16 September 2006|url-status=dead|archive-url=https://web.archive.org/web/20060928091032/http://www.iau.org/PLANETS_AROUND_OTHER_STARS.247.0.html|archive-date=28 September 2006}}</ref> the issue of which convention is 'correct' remains open, however subsequent scientific publications about this system appear to have adopted the Pepe ''et al.'' system, as has the system's entry in the [[Extrasolar Planets Encyclopaedia]].<ref>{{cite journal|bibcode=2008MNRAS.386L..43S|title=New solutions for the planetary dynamics in HD160691 using a Newtonian model and latest data|author=Short, D. |author2=Windmiller, G. |author3=Orosz, J. A.|journal=[[Monthly Notices of the Royal Astronomical Society|MNRAS]]|volume=386|issue=1|pages=L43–L46|doi=10.1111/j.1745-3933.2008.00457.x|year=2008|arxiv = 0802.1781 }}</ref><ref>{{cite encyclopedia |url=http://exoplanet.eu/star.php?st=HD+160691 |title=Notes for star HD 160691 |access-date=11 April 2009 |encyclopedia=Title Extrasolar Planets Encyclopaedia |url-status=dead |archive-url=https://web.archive.org/web/20081222144505/http://exoplanet.eu/star.php?st=HD+160691 |archive-date=22 December 2008 }}</ref>

In July 2014 the [[International Astronomical Union]] launched a process for giving proper names to certain exoplanets and their host stars.<ref>[http://www.iau.org/news/pressreleases/detail/iau1404/ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars]. IAU.org. 9 July 2014</ref> The process involved public nomination and voting for the new names.<ref>[http://nameexoworlds.iau.org/process NameExoWorlds The Process]</ref> In December 2015, the IAU announced the winning names were Cervantes for this star and Quijote, Dulcinea, Rocinante and Sancho, for its planets (b, c, d, and e, respectively; the IAU used the Pepe ''et al'' system).<ref>[http://www.iau.org/news/pressreleases/detail/iau1514/ Final Results of NameExoWorlds Public Vote Released], International Astronomical Union, 15 December 2015.</ref><ref>[http://nameexoworlds.iau.org/systems/106 The Proposals page for Mu Arae], International Astronomical Union, 3 January 2016.</ref>

The winning names were those submitted by the Planetario de Pamplona, Spain. [[Miguel de Cervantes]] Saavedra (1547–1616) was a famous Spanish writer and author of ''[[Don Quixote|El Ingenioso Hidalgo Don Quixote de la Mancha]]''. The planets are named after characters of that novel: Quijote was the lead character; [[Dulcinea del Toboso|Dulcinea]] his love interest; [[Rocinante]] his horse, and [[Sancho Panza|Sancho]] his [[squire]].<ref>[http://www.nameexoworlds.iau.org/approved-names#comp-jwdpj57w NameExoWorlds The Approved Names]</ref>

In 2016, the IAU organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> to catalog and standardize proper names for stars. In its first bulletin of July 2016,<ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN"/>

== Stellar characteristics ==

According to measurements made by the [[Hipparcos]] [[astrometry|astrometric]] [[satellite]], Mu Arae exhibits a [[parallax]] of 64.47 [[Minute of arc|milliarcsecond]]s as the Earth moves around the Sun. When combined with the known distance from the Earth to the Sun, this means the star is located at a distance of 50.6 [[light year]]s (15.51 [[parsec]]s).<ref name=aaa474_2_653/><ref group="note">The formula for converting parallax to distance is <math>\scriptstyle\mathrm{Distance\ in\ parsecs}=\frac{1}{\mathrm{parallax\ in\ arcseconds}}</math></ref> Seen from Earth it has an [[apparent magnitude]] of +5.12 and is visible to the [[naked eye]].

[[Asteroseismology|Asteroseismic]] analysis of the star reveals it is approximately 10% more massive than the Sun and significantly older, at around 6.34 billion years. The radius of the star is 36% greater than that of the Sun and it is 90% more luminous. The star contains twice the abundance of iron relative to [[hydrogen]] of the Sun and is therefore described as [[metal-rich]]. Mu Arae is also more enriched than the Sun in the element [[helium]].<ref name="soriano2009" />

Mu Arae has a listed [[stellar classification|spectral type]] of G3IV–V.<ref name=aj132_1_161/> The G3 part means the star is similar to the Sun (a G2V star). The star may be entering the [[subgiant]] stage of its evolution as it starts to run out of [[hydrogen]] in its core. This is reflected in its uncertain [[luminosity class]], between IV (the subgiants) and V ([[main sequence]] [[dwarf star]] stars like the Sun).

== Planetary system ==
[[File:Mu Arae system.jpg|thumb|right|The Mu Arae star with distance relationships for its four planets]]
[[File:MuAraeOuterOrbits.svg|thumb|right|220px|The orbits of the outer three planets in the Mu Arae system compared with those in the [[Solar System]]. Central star is not to scale. At the scale of this picture, the innermost planet would be located at the edge of the disc representing the central star.]]

=== Discovery ===
In 2001, an extrasolar planet was announced by the [[Anglo-Australian Planet Search]] team, together with the planet orbiting [[Epsilon Reticuli]]. The planet, designated [[Mu Arae b]], was thought to be in a highly [[eccentricity (orbit)|eccentric]] orbit of around 743 days.<ref>{{cite journal | author=Butler | title=Two New Planets from the Anglo-Australian Planet Search | journal=The Astrophysical Journal | volume=555 | issue=1 |year=2001 | pages=410–417 | doi=10.1086/321467 | last2=Tinney | first2=C. G. | last3=Marcy | first3=Geoffrey W. | last4=Jones | first4=Hugh R. A. | last5=Penny | first5=Alan J. | last6=Apps | first6=Kevin | bibcode=2001ApJ...555..410B| hdl=2299/137 | hdl-access=free }}</ref> The discovery was made by analysing variations in the star's [[radial velocity]] (measured by observing the [[Doppler shift]] of the star's [[spectral line]]s) as a result of being pulled around by the planet's [[gravity]]. Further observations revealed the presence of a second object in the system (now designated as [[Mu Arae e]]), which was published in 2004. At the time, the parameters of this planet were poorly constrained and it was thought to be in an orbit of around 8.2 years with a high eccentricity.<ref name="McCarthy2004"/> Later in 2004, a small inner planet designated [[Mu Arae c]] was announced with a mass comparable with that of [[Uranus]] in a 9-day orbit. This was the first of the class of planets known as "[[hot Neptune]]s" to be discovered. The discovery was made by making high-precision radial velocity measurements with the [[High Accuracy Radial Velocity Planet Searcher]] (HARPS) [[spectrograph]].<ref name="santos">{{cite journal|bibcode=2004A&A...426L..19S |last=Santos |first=N. C. |title=The HARPS survey for southern extra-solar planets II. A 14 Earth-masses exoplanet around μ Arae|journal=[[Astronomy and Astrophysics]]|volume=426 |issue=1|year=2004|pages=L19 – L23|doi=10.1051/0004-6361:200400076 |last2=Bouchy|first2=F. |last3=Mayor|first3=M. |last4=Pepe|first4=F. |last5=Queloz|first5=D. |last6=Udry|first6=S. |last7=Lovis|first7=C. |last8=Bazot|first8=M. |last9=Benz|first9=W. |last10=Bertaux|first10=J.-L. |last11=Lo Curto|first11=G. |last12=Delfosse|first12=X. |last13=Mordasini|first13=C. |last14=Naef|first14=D. |last15=Sivan|first15=J.-P. |last16=Vauclair|first16=S. |arxiv = astro-ph/0408471 |display-authors=8}}</ref>

In 2006, two teams, one led by [[Krzysztof Goździewski]] and the other by [[Francesco Pepe]] independently announced four-planet models for the radial velocity measurements of the star, with a new planet ([[Mu Arae d]]) in a near-circular orbit lasting approximately 311 days.<ref name="gozdziewski">{{Cite journal|author=Gozdziewski, K.|title=On the extrasolar multi-planet system around HD160691|journal=The Astrophysical Journal|volume=657|issue=1|pages=546–558|year=2007|arxiv=astro-ph/0608279|last2= Maciejewski|first2=Andrzej J.|last3=Migaszewski|first3=Cezary|doi=10.1086/510554|bibcode = 2007ApJ...657..546G }}</ref><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 }}</ref> The new model gives revised parameters for the previously known planets, with lower eccentricity orbits than in the previous model and including a more robust characterization of the orbit of Mu Arae e. The discovery of the fourth planet made Mu Arae the second known four-planet extrasolar system, after [[55 Cancri]].

=== System architecture and habitability ===
The Mu Arae system consists of an inner Uranus-mass planet in a tight 9-day orbit and three massive planets, probably gas giants, on wide, near-circular orbits, which contrasts with the high-eccentricity orbits typically observed for long-period extrasolar planets. The Uranus-mass planet may be a [[chthonian planet]], the [[planetary core|core]] of a gas giant which has had its outer layers stripped away by stellar radiation.<ref>{{cite journal|bibcode=2006A&A...450.1221B |author=Baraffe, I.|title=Birth and fate of hot-Neptune planets|journal=[[Astronomy and Astrophysics]]|volume=450|issue=3|year=2006|pages=1221–1229|doi=10.1051/0004-6361:20054040|arxiv = astro-ph/0512091 |last2=Alibert|first2=Y.|last3=Chabrier|first3=G.|last4=Benz|first4=W.}}</ref> Alternatively it may have formed in the inner regions of the Mu Arae system as a rocky "super-Earth".<ref name="santos"/> The inner gas giants "d" and "b" are located close to the 2:1 [[orbital resonance]] which causes them to undergo strong interactions. The best-fit solution to the system is actually unstable:<ref>{{cite journal |last1=Agnew |first1=Matthew T |last2=Maddison |first2=Sarah T |last3=Horner |first3=Jonathan |last4=Kane |first4=Stephen R |title=Predicting multiple planet stability and habitable zone companions in the TESS era |journal=Monthly Notices of the Royal Astronomical Society |date=June 2019 |volume=485 |issue=4 |pages=4703–4725 |doi=10.1093/mnras/stz345 |url=https://academic.oup.com/mnras/article/485/4/4703/5307090 |access-date=28 April 2020|doi-access=free }}</ref> simulations suggest the system is destroyed after 78 million years, which is significantly shorter than the estimated age of the star system. More stable solutions, including ones in which the two planets are actually in the resonance (similar to the situation in the [[Gliese 876]] system) can be found which give only a slightly worse fit to the data.<ref name="pepe"/> Searches for [[circumstellar disc]]s show no evidence for a debris disc similar to the [[Kuiper belt]] around Mu Arae. If Mu Arae does have a Kuiper belt, it is too faint to be detected with current instruments.<ref>{{cite journal|bibcode=2004A&A...424..613S |author=Schütz, O.|title=A search for circumstellar dust disks with ADONIS|journal=[[Astronomy and Astrophysics]]|volume=424 |issue=2|year=2004|pages=613–618|doi=10.1051/0004-6361:20034215|arxiv = astro-ph/0408530 |last2=Bönhardt|first2=H.|last3=Pantin|first3=E.|last4=Sterzik|first4=M.|last5=Els|first5=S.|last6=Hahn|first6=J.|last7=Henning|first7=Th.}}</ref>

The gas giant planet "b" is located in the liquid water habitable zone of Mu Arae. This would prevent an Earth-like planet from forming in the habitable zone, however large [[natural satellite|moons]] of the gas giant could potentially support liquid water.{{Synthesis inline|date=January 2016}} On the other hand, it is unclear whether such massive moons could actually form around a gas giant planet, thanks to an apparent scaling law between the mass of the planet and its satellite system.<ref>{{cite journal|doi= 10.1038/nature04860|author=Canup, R. |author2=Ward, W.|title=A common mass scaling for satellite systems of gaseous planets|journal=[[Nature (journal)|Nature]]|volume=441|year=2006|pages=834–839|pmid= 16778883|issue= 7095|bibcode = 2006Natur.441..834C }}</ref> In addition, measurements of the star's [[ultraviolet]] [[flux]] suggest that any potentially [[planetary habitability|habitable]] planets or moons may not receive enough ultraviolet to trigger the formation of [[biomolecule]]s.<ref name="buccino">{{cite journal|bibcode=2006Icar..183..491B|author=Buccino, A.|title=Ultraviolet Radiation Constraints around the Circumstellar Habitable Zones|journal=[[Icarus (journal)|Icarus]]|volume=183|issue=2|pages=491–503|year=2006|doi=10.1016/j.icarus.2006.03.007|arxiv = astro-ph/0512291 |last2=Lemarchand|first2=Guillermo A.|last3=Mauas|first3=Pablo J.D.}}</ref> Planet "d" would receive a similar amount of ultraviolet to the Earth and thus lies in the [[ultraviolet habitable zone]]. However, it would be too hot for any moons to support surface liquid water.

{{OrbitboxPlanet begin
| table_ref=<ref name="pepe" />
}}
{{OrbitboxPlanet
| exoplanet = [[Mu Arae c|c (Dulcinea)]]
| mass_earth = >10.5551
| period = 9.6386 ± 0.0015
| semimajor = 0.09094
| eccentricity = 0.172 ± 0.04
}}
{{OrbitboxPlanet
| exoplanet = [[Mu Arae d|d (Rocinante)]]
| mass = >0.5219
| period = 310.55 ± 0.83
| semimajor = 0.921
| eccentricity = 0.0666 ± 0.0122
}}
{{OrbitboxPlanet
| exoplanet = [[Mu Arae b|b (Quijote)]]
| mass = >1.676
| period = 643.25 ± 0.90
| semimajor = 1.497
| eccentricity = 0.128 ± 0.017
}}
{{OrbitboxPlanet
| exoplanet = [[Mu Arae e|e (Sancho)]]
| mass = >1.814
| period = 4205.8 ± 758.9
| semimajor = 5.235
| eccentricity = 0.0985 ± 0.0627
}}
{{Orbitbox end}}

== See also ==
* [[55 Cancri]]
* [[Extrasolar planet]]
* [[List of extrasolar planets]]
* [[PSR 1257+12]]

== Notes ==
<references group="note" />

== References ==
{{Reflist|refs=
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<ref name=aj132_1_161>{{Cite journal| display-authors=1 | last1=Gray | first1=R. O. | first2=C. J. | last2=Corbally | first3=R. F. | last3=Garrison | first4=M. T. | last4=McFadden | last5=Bubar | first5=E. J. | last6=McGahee | first6=C. E. | last7=O'Donoghue | first7=A. A. | last8=Knox | first8=E. R. | title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I | journal=The Astronomical Journal | volume=132 | issue=1 | pages=161–170 |date=July 2006 | doi=10.1086/504637 | bibcode=2006AJ....132..161G |arxiv = astro-ph/0603770 }}</ref>

<ref name=Anderson2012>{{cite journal
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| journal=Astronomy Letters
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<ref name=ibsh8_30>{{Cite journal| last1=Feinstein | first1=A. | title=Photoelectric observations of Southern late-type stars | journal=The Information Bulletin for the Southern Hemisphere | volume=8 | page=30 |year=1966 | bibcode=1966IBSH....8...30F }}</ref>

<ref name=scfs>{{Cite journal| display-authors=1 | title=Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions | journal=Veröff. Astron. Rechen-Inst. Heidelb | volume=35 | last1=Wielen | first1=R. | last2=Schwan | first2=H. | last3=Dettbarn | first3=C. | last4=Lenhardt | first4=H. | last5=Jahreiß | first5=H. | last6=Jährling | first6=R. | publisher=Astronomisches Rechen-Institut Heidelberg | issue=35 | pages=1 |year=1999 | bibcode=1999VeARI..35....1W }}</ref>

<ref name="McCarthy2004">{{cite journal | title=Multiple Companions to HD 154857 and HD 160691 | last1=McCarthy | first1=Chris | last2=Butler | first2=R. Paul | last3=Tinney | first3=C. G. | last4=Jones | first4=Hugh R. A. | last5=Marcy | first5=Geoffrey W. | last6=Carter | first6=Brad | last7=Penny | first7=Alan J. | last8=Fischer | first8=Debra A. | display-authors=1 | journal=The Astrophysical Journal | volume=617 | issue=1 | pages=575–579 |year=2004 | arxiv=astro-ph/0409335 | bibcode=2004ApJ...617..575M | doi=10.1086/425214 }}</ref>

<ref name=mnras405_3_1907>{{Cite journal| display-authors=1 | last1=Bruntt | first1=H. | last2=Bedding | first2=T. R. | last3=Quirion | first3=P.-O. | last4=Lo Curto | first4=G. | last5=Carrier | first5=F. | last6=Smalley | first6=B. | last7=Dall | first7=T. H. | last8=Arentoft | first8=T. | last9=Bazot | first9=M. | last10=Butler | first10=R. P. | title=Accurate fundamental parameters for 23 bright solar-type stars | journal=Monthly Notices of the Royal Astronomical Society | volume=405 | issue=3 | pages=1907–1923 |date=July 2010 | doi=10.1111/j.1365-2966.2010.16575.x | bibcode=2010MNRAS.405.1907B |arxiv = 1002.4268 }}</ref>

}}

== External links ==
{{Commons category|Mu Arae}}
* [http://webviz.u-strasbg.fr/viz-bin/VizieR-S?GJ%20691 GJ 691]
* [http://webviz.u-strasbg.fr/viz-bin/VizieR-S?HR%206585 HR 6585]
* {{cite web |url=http://www.space.com/scienceastronomy/super_earth_040825.html |title='Super Earth' Discovered at Nearby Star |access-date=17 July 2008 |work=[[Space.com]] |date=25 August 2004 |first=Robert Roy |last=Britt }}
* {{cite web |url=http://www.eso.org/public/outreach/press-rel/pr-2004/pr-22-04.html |title=Fourteen Times the Earth |access-date=17 July 2008 |work=[[European Southern Observatory]] |date=25 August 2004 |url-status=dead |archive-url=https://web.archive.org/web/20070607190706/http://www.eso.org/public/outreach/press-rel/pr-2004/pr-22-04.html |archive-date=7 June 2007 }}
* {{cite web |url=http://obswww.unige.ch/Exoplanets/hd160691.html |title=Mu Ara: a system with 4 planets |access-date=17 July 2008 |work=Geneva Observatory }}
* {{cite web |url=http://www.solstation.com/stars2/mu-arae.htm |title=Mu Arae |access-date=17 July 2008 |work=SolStation }}
* [http://aladin.u-strasbg.fr/AladinPreview?-c=17+44+08.7029-51+50+02.591&ident=LTT++7053&submit=Aladin+previewer Image Mu Arae]
* [http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ Extrasolar Planet Interactions] by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona
{{clear}}
{{Mu Arae|state=collapsed}}

{{Stars of Ara}}
{{Sky|17|44|08.7|-|51|50|03|49.8}}

{{Good article}}

{{DEFAULTSORT:Mu Arae}}
[[Category:Ara (constellation)]]
[[Category:Bayer objects|Arae, Mu]]
[[Category:Durchmusterung objects|CD-51 11094]]
[[Category:G-type main-sequence stars]]
[[Category:G-type subgiants]]
[[Category:Gliese and GJ objects|0691]]
[[Category:Henry Draper Catalogue objects|160691]]
[[Category:Hipparcos objects|086796]]
[[Category:HR objects|6585]]
[[Category:Planetary systems with four confirmed planets]]

47 tucanae

2021-03-07T23:29:52Z

JDuntemann: Created page with "{{ Infobox globular cluster | | name = 47 Tucanae | image = 300px | caption = After Omega Centauri, 47 Tucanae is the brightest globu..."

{{ Infobox globular cluster |
| name = 47 Tucanae
| image = [[Image:Globular cluster 47 Tucanae.jpg|300px]]
| caption = After Omega Centauri, 47 Tucanae is the brightest globular cluster in the night sky.<ref>{{cite web|title=Retirement in the suburbs|url=http://www.spacetelescope.org/news/heic1510/|accessdate=12 June 2015}}</ref>
| epoch = [[J2000]]
| class = III<ref name=hcob849_11/>
| ra = {{RA|00|24|05.67}}<ref name="simbad"/>
| dec = {{DEC|–72|04|52.6}}<ref name="simbad" />
| dist_ly = {{Convert|16.70|+/-|0.85|kly|kpc|abbr=on|lk=on|sigfig=2}}<ref name="Carretta et al. 2000"/>
| appmag_v = +4.91<ref name="simbad" />
| size_v = 30′.9
| constellation = [[Tucana]]
| mass_kg =
| mass_msol = {{Val|7.00|e=5}}<ref name=mnras406_3_2000/>
| radius_ly = 60 ly<ref>distance × sin( diameter_angle / 2 ) = 60 ly. radius</ref>
| v_hb = 14.2
| metal_fe = –0.78<ref name=mnras404_3_1203/>
| age = 13.06 [[Gigayear|Gyr]]<ref name=mnras404_3_1203/>
| notes = 2nd brightest globular cluster after [[Omega Centauri]]
| names = [[Bayer designation|ξ Tuc]], [[New General Catalogue|NGC]] 104, GCl 1<ref name="simbad" /> [[1RXS]] J002404.6-720456
}}

'''47 Tucanae''' ('''NGC 104''') or just '''47 Tuc''' is a [[globular cluster]] located in the [[constellation]] [[Tucana]]. It is about 16,700 [[light year]]s away from [[Earth]], and 120 light years across. It can be seen with the [[naked eye]], with a visual [[apparent magnitude]] of 4.9. Its number comes not from the [[Flamsteed]] catalogue, but the more obscure 1801 "Allgemeine Beschreibung und Nachweisung der Gestirne nebst Verzeichniss" compiled by [[Johann Elert Bode]].

==Characteristics==
It is the second brightest globular cluster in the sky (after [[Omega Centauri]]), and is noted for having a very bright and dense core. It is also one of the most massive globular clusters in the Galaxy, containing millions of stars. The cluster appears roughly the size of the full [[moon]] in the sky under ideal conditions.

The core of 47 Tucanae was the subject of a major survey for [[planet]]s, using the [[Hubble Space Telescope]] to look for partial [[eclipse]]s of stars by their planets. No planets were found, though 10-15 were expected based on the rate of planet discoveries around stars near the Sun. This indicates that planets are relatively rare in globular clusters.<ref>{{cite web | title=A Shortage of Planets |accessdate=16 November 2010 | url= http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=192}}</ref> A later ground-based survey in the uncrowded outer regions of the cluster also failed to detect planets when several were expected. This strongly indicates that the low [[metallicity]] of the environment, rather than the crowding, is responsible.

47 Tucanae's dense core contains a number of exotic stars of scientific interest. Globular clusters efficiently sort stars by mass, with the most massive stars falling to the center.<ref>{{cite web | title= Mass Migration: How Stars Move in Crowd | last= Bryner | first= Jeanna | accessdate = 14 November 2010 | url = http://www.space.com/scienceastronomy/061030_mm_star_migration.html}}</ref>
47 Tucanae contains at least 21 [[blue straggler]]s near its core.<ref>{{cite news | title=NASA's Hubble Space Telescope Finds "Blue Straggler" Stars in the Core of a Globular Cluster | publisher=Hubble News Desk | date=1991-07-24 | url=http://hubblesite.org/newscenter/newsdesk/archive/releases/1991/12/text/ | accessdate=2006-05-24 }}</ref>
It also contains hundreds of X-ray sources, including stars with enhanced [[chromospheric activity]] due to their presence in [[binary star]] systems, [[cataclysmic variable star]]s containing [[white dwarf]]s accreting from companion stars, and [[low-mass X-ray binaries]] containing [[neutron star]]s that are not currently accreting, but can be observed by the [[X-rays]] emitted from the hot surface of the neutron star.<ref>{{cite journal
| doi = 10.1126/science.1061135
| last1 = Grindlay | first1 = Jonathan E.
| last2 = Heinke | first2 = Craig O.
| last3 = Edmonds | first3 = Peter D.
| last4 = Murray | first4= Steve S.
| title= High-Resolution X-ray Imaging of a Globular Cluster Core: Compact Binaries in 47Tuc
| journal = Science
| volume = 292 | issue = 5525
| pages = 2290–2295
| date = 2001
| pmid = 11358997
| bibcode=2001Sci...292.2290G|arxiv = astro-ph/0105528 }}</ref>
47 Tucanae has 23 known [[millisecond pulsar]]s, the second largest population of [[pulsar]]s in any globular cluster.<ref>{{cite web | title=The 23 millisecond radio pulsars in 47 Tucanae | url=http://www.naic.edu/~pfreire//47Tuc/}}</ref>
These pulsars are thought to be spun up by the [[Accretion (astrophysics)|accretion]] of material from binary companion stars, in a previous [[X-ray binary]] phase. The companion of one pulsar in 47 Tucanae, 47 Tucanae W, seems to still be transferring mass towards the [[neutron star]], indicating that this system is completing a transition from being an accreting [[low-mass X-ray binary]] to a [[millisecond pulsar]].<ref>{{cite journal
| last1 = Bogdanov | first1 = Slavko
| last2 = Grindlay | first2 = Jonathan E.
| last3 = van den Berg | first3 = Maureen
| title= An X-Ray Variable Millisecond Pulsar in the Globular Cluster 47 Tucanae: Closing the Link to Low-Mass X-Ray Binaries
| journal = Astrophysical Journal
| volume = 630 | issue = 2
| pages = 1029–1036
| date = 2005
| bibcode=2005ApJ...630.1029B|arxiv = astro-ph/0506031 |doi = 10.1086/432249 }}</ref>
X-ray emission has been individually detected from most millisecond pulsars in 47 Tucanae with the [[Chandra X-ray Observatory]], likely emission from the neutron star surface,<ref>{{cite journal
| doi = 10.1086/505133
| last1 = Bogdanov | first1 = Slavko
| last2 = Grindlay | first2 = Jonathan E.
| last3 = Heinke | first3 = Craig O.
| last4 = Camilo | first4= Fernando
| last5 = Freire | first5= Paulo C. C.
| last6 = Becker | first6 = Werner
| title= Chandra X-Ray Observations of 19 Millisecond Pulsars in the Globular Cluster 47 Tucanae
| journal = Astrophysical Journal
| volume = 646 | issue = 2
| pages = 1104–1115
| date = 2006
| bibcode=2006ApJ...646.1104B|arxiv = astro-ph/0604318 }}</ref>
and gamma-ray emission has been detected with the [[Fermi Gamma-ray Space Telescope]] from its millisecond pulsar population (making 47 Tucanae the first globular cluster to be detected in gamma-rays).<ref>{{Cite journal | last1 = Abdo | first1 = A. A. | last2 = Ackermann | first2 = M. | last3 = Ajello | first3 = M. | last4 = Atwood | first4 = W. B. | last5 = Axelsson | first5 = M. | last6 = Baldini | first6 = L. | last7 = Ballet | first7 = J. | last8 = Barbiellini | first8 = G. | last9 = Bastieri | first9 = D. | last10 = Baughman | first10 = B. M. | last11 = Bechtol | first11 = K. | last12 = Bellazzini | first12 = R. | last13 = Berenji | first13 = B. | last14 = Blandford | first14 = R. D. | last15 = Bloom | first15 = E. D. | last16 = Bonamente | first16 = E. | last17 = Borgland | first17 = A. W. | last18 = Bregeon | first18 = J. | last19 = Brez | first19 = A. | last20 = Brigida | first20 = M. | last21 = Bruel | first21 = P. | last22 = Burnett | first22 = T. H. | last23 = Caliandro | first23 = G. A. | last24 = Cameron | first24 = R. A. | last25 = [[Patrizia A. Caraveo|Caraveo]] | first25 = P. A. | last26 = Casandjian | first26 = J. M. | last27 = Cecchi | first28 = O. | first29 = E. | last30 = Chaty | first30 = S. | last28 = Celik | last29 = Charles | first27 = C. | title = Detection of High-Energy Gamma-Ray Emission from the Globular Cluster 47 Tucanae with Fermi | doi = 10.1126/science.1177023 | journal = Science | volume = 325 | issue = 5942 | pages = 845–848 | year = 2009 | pmid = 19679807| pmc =
|bibcode = 2009Sci...325..845A }}</ref>

There is no evidence yet for the existence of any [[black hole]]s in 47 Tucanae; [[Hubble Space Telescope]] data provides the strongest constraint on the mass of any possible black hole at its center, < 1500 times the mass of our Sun.<ref>{{cite journal
| doi = 10.1086/505692
| last1 = McLaughlin
| first1 = Dean E.
| last2 = Anderson
| first2 = Jay
| last3 = Meylan
| first3 = Georges
| last4 = Gebhardt
| first4 = Karl
| last5 = Pryor
| first5 = Carlton
| last6 = Minniti
| first6 = Dante
| last7 = Phinney
| first7 = Sterl
| title= Hubble Space Telescope Proper Motions and Stellar Dynamics in the Core of the Globular Cluster 47 Tucanae
| journal = Astrophysical Journal Supplement
| volume = 166 | issue = 1
| pages = 249–297
| date = 2006
| bibcode=2006ApJS..166..249M|arxiv = astro-ph/0607597 }}</ref>

==History==
47 Tucanae was discovered by [[Nicolas Louis de Lacaille]] in 1751, who thought it was the nucleus of a bright comet.<ref name="o'meara">{{cite book |title=Deep-Sky Companions: Southern Gems |first=Stephen James |last=O'Meara |publisher=Cambridge University Press|location=Cambridge, United Kingdom |date=2013 |pages=16–17 |isbn=9781107015012|url=http://books.google.com.au/books?id=S5QIEKns33sC&pg=PA17&dq=47+Tucanae&hl=en&sa=X&ei=7SxsUu7AOej_iAeI24GIDw&ved=0CEkQ6AEwBQ#v=onepage&q=47%20Tucanae&f=false}}</ref> Its southern location had hidden it from European observers until then.

In December 2008, [[Ragbir Bhathal]] of the [[University of Western Sydney]] claimed the detection of a strong laser-like signal from the direction of 47 Tucanae.<ref>{{cite web | title=The Australian Optical SETI Project | url=http://www.lpi.usra.edu/meetings/abscicon2010/pdf/5046.pdf}}</ref>

In May 2015, the first observations of the process of [[mass segregation]] in this globular cluster were announced.<ref name=SpaceDaily-2015-05-18>{{cite news |url= http://www.spacedaily.com/reports/Hubble_Catches_Stellar_Exodus_in_Action_999.html |title= Hubble Catches Stellar Exodus in Action |date= 18 May 2015 |publisher= Space Daily }}</ref>

==Gallery==
<gallery>
File:Hubble finds evidence of multiple stellar populations in globular cluster 47 Tucanae.jpg|Evidence of multiple stellar populations<ref>{{cite web|title=Hubble finds evidence of multiple stellar populations in globular cluster 47 Tucanae|url=http://www.spacetelescope.org/images/opo1325a/|work=Image Gallery|publisher=ESA/Hubble|accessdate=15 August 2013}}</ref>
File:The Globular Cluster 47 Tu.jpg|Globular Cluster 47 Tuc. Credit [[ESO]]
File:A close look at the globular star cluster 47 Tucanae.ogg|Sequence pans across a wide view of the region surrounding the [[Small Magellanic Cloud|SMC]].
</gallery>

==References==
{{reflist|refs=

<ref name=mnras404_3_1203>{{citation | last1=Forbes | first1=Duncan A. | last2=Bridges | first2=Terry | title=Accreted versus in situ Milky Way globular clusters | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=404 | issue=3 | pages=1203–1214 | doi=10.1111/j.1365-2966.2010.16373.x | bibcode=2010MNRAS.404.1203F | postscript=. |arxiv = 1001.4289 |date=May 2010}}</ref>

<ref name=mnras406_3_2000>{{citation | last1=Marks | first1=Michael | last2=Kroupa | first2=Pavel | title=Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way | journal=Monthly Notices of the Royal Astronomical Society | volume=406 | issue=3 | pages=2000–2012 | doi=10.1111/j.1365-2966.2010.16813.x | bibcode=2010MNRAS.406.2000M | postscript=. |arxiv = 1004.2255 |date=August 2010}} Mass is from M<sub>PD</sub> on Table 1.</ref>

<ref name=hcob849_11>{{citation | last1=Shapley | first1=Harlow | last2=Sawyer | first2=Helen B. | title=A Classification of Globular Clusters | journal=Harvard College Observatory Bulletin | issue=849 | pages=11–14 | bibcode=1927BHarO.849...11S | postscript=. |date=August 1927}}</ref>

<ref name = "Carretta et al. 2000">{{Cite journal | title=Distances, Ages, and Epoch of Formation of Globular Clusters | journal=The Astrophysical Journal | url=http://adsabs.harvard.edu/abs/2000ApJ...533..215C | bibcode=2000ApJ...533..215C | accessdate=2008-11-12 |arxiv = astro-ph/9902086 |doi = 10.1086/308629 }}</ref>

<ref name="simbad">{{cite web | title=SIMBAD Astronomical Database | work=Results for NGC 104 | url=http://simbad.u-strasbg.fr/Simbad | accessdate=2006-11-17 }}</ref>

}}

==External links==
{{commons category|47_Tuc|47 Tucanae}}
*[http://www.spacetelescope.org/news/heic0616/ 47 Tucanae at the ESA-Hubble website]
*[http://gclusters.altervista.org/cluster_4.php?ggc=47+Tuc 47 Tucanae, Galactic Globular Clusters Database page]
*[http://chandra.harvard.edu/photo/2005/47tuc/ 47 Tucanae at the Chandra X-ray Observatory website]

{{Catalogs | NGC = 104 | C = 106}}
{{Stars of Tucana}}

[[Category:Globular clusters]]
[[Category:Tucana (constellation)]]
[[Category:Bayer objects|Tucanae, Xi]]
[[Category:Flamsteed objects|Tucanae, 47]]
[[Category:NGC objects|Xi Tucanae]]
[[Category:Caldwell objects|106b]]
[[Category:Astronomical objects discovered in 1751|17510914]]
[[Category:Articles containing video clips]]

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2021-03-02T19:13:39Z

JDuntemann:

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