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| {{Starbox begin
| | The author is known by the name of Figures Wunder. North Dakota is our beginning place. Doing ceramics is what my family and I enjoy. He used to be unemployed but now he is a computer operator but his marketing never arrives.<br><br>Also visit my blog: [http://linkingtear.com/profile-10764/info/ linkingtear.com] |
| | name = Mu Arae
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| }}
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| {{Starbox image
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| | image = [[Image:Mu Arae NS1744m5150-dss-1987.jpg|250px|Mu Arae (NASA Nstars database)]]
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| | caption = Mu Arae
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| }}
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| {{Starbox observe
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| | epoch = J2000.0
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| | constell = [[Ara (constellation)|Ara]]
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| | ra = {{RA|17|44|08.70114}}<ref name=aaa474_2_653/>
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| | dec = {{DEC|−51|50|02.5853}}<ref name=aaa474_2_653/>
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| | appmag_v = +5.12
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| }}
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| {{Starbox character
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| | class = G3IV–V<ref name=aj132_1_161/>
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| | b-v = +0.70<ref name=ibsh8_30/>
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| | u-b = +0.24<ref name=ibsh8_30/>
| |
| | r-i = 0.2
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| | v-r =
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| | variable =
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| }}
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| {{Starbox astrometry
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| | radial_v = −9.0<ref name=scfs/>
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| | prop_mo_ra = −16.85<ref name=aaa474_2_653/>
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| | prop_mo_dec = −190.60<ref name=aaa474_2_653/>
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| | parallax = 64.47
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| | p_error = 0.31
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| | parallax_footnote = <ref name=aaa474_2_653/>
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| | absmag_v = +4.28
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| }}
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| {{Starbox detail
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| | age_gyr = {{nowrap|6.34 ± 0.40}}<ref name="soriano2009">{{cite arXiv|title=New seismic analysis of the exoplanet-host star Mu Arae|eprint=0903.5475|class=astro-ph|year=2009|last1=Soriano | first1=M.|last2=Vauclair | first2=S.}}</ref>
| |
| | metal = {{nowrap|200 ± 5%}}<ref name="soriano2009" /><ref group="note">From [Fe/H] = 0.30 ± 0.01</ref>
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| | metal_fe = {{nowrap|0.30 ± 0.01}}<ref name="soriano2009" />
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| | mass = {{nowrap|1.10 ± 0.01}}<ref name="soriano2009" />
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| | radius = {{nowrap|1.36 ± 0.01}}<ref name="soriano2009" />
| |
| | rotation = 31 days
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| | rotational_velocity = 1.4<ref name=mnras405_3_1907/>
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| | gravity = 4.19<ref name=aj132_1_161/>
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| | luminosity = {{nowrap|1.90 ± 0.10}}<ref name="soriano2009" />
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| | temperature = {{nowrap|5820 ± 40}}<ref name="soriano2009" />
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| }}
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| {{Starbox catalog
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| | names = [[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
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| }}
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| {{Starbox reference
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| | Simbad = LTT+7053
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| | ARICNS = 01434
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| | NSTED = Mu+Arae
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| | EPE = mu+Ara
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| }}
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| {{Starbox end}}
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| '''Mu Arae''' (μ Ara, μ Arae), often referred to by its designation in the [[Henry Draper catalogue]] '''HD 160691''', is a [[main sequence]] [[G V star|G-type]] [[star]] around 50 [[light-year]]s away from Earth in the [[constellation]] of [[Ara (constellation)|Ara]]. The star has a [[planetary system]] with four known planets, three of them with masses comparable to that of [[Jupiter]]. The system's innermost planet was the first "hot Neptune or super-Earth" to be discovered.
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| == Distance and visibility ==
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| 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]].
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| == Stellar characteristics ==
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| [[Asteroseismology|Asteroseismic]] analysis of the star reveals it is approximately 10% more massive than the Sun and significantly older, at around 6,340 million 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 our Sun and is therefore described as [[metal-rich]]. Mu Arae is also more enriched than the Sun in the element [[helium]].<ref name="soriano2009" />
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| 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 our 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).
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| == Planetary system ==
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| [[File:MuAraeOuterOrbits.svg|thumb|left|250px|The orbits of the outer three planets in the Mu Arae system compared to those in our 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.]]
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| === Discovery ===
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| 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 | url=http://www.iop.org/EJ/article/0004-637X/555/1/410/53257.html | author=Butler ''et al.'' | 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}}</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 to 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 |author=Santos ''et al.''|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.|arxiv = astro-ph/0408471 }}</ref>
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| 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 arXiv|author=Gozdziewski, K. ''et al.''|title=On the extrasolar multi-planet system around HD160691|year=2006|eprint=astro-ph/0608279}}</ref><ref name="pepe">{{cite arXiv|author=Pepe, F. ''et al.''|title=The HARPS search for southern extra-solar planets. IX. μ Ara, a system with four planets|year=2006|eprint=astro-ph/0608396}}</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]].
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| === System architecture and habitability ===
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| 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. ''et al.''|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 }}</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: 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. ''et al.''|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 }}</ref>
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| 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. 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., 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=2005astro.ph.12291B|author=Buccino, A. ''et al.''|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 }}</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.
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| === Planet designations ===
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| The established convention for extrasolar planets is that the planets receive lower-case [[Latin alphabet|Roman letters]] starting from "b", in order of discovery. This system is used by the team led by Goździewski.<ref name="gozdziewski"/> On the other hand, the team led by Pepe have 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|accessdate=16 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.; Windmiller, G.; 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 web |url=http://exoplanet.eu/star.php?st=HD+160691 |title=Notes for star HD 160691 |accessdate=2009-04-11|work=Title Extrasolar Planets Encyclopaedia}}</ref>
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| {{OrbitboxPlanet begin
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| | table_ref=<ref name="pepe" />
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| }}
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| {{OrbitboxPlanet
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| | exoplanet = [[Mu Arae c|c]]
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| | mass = >0.03321
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| | period = 9.6386 ± 0.0015
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| | semimajor = 0.09094
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| | eccentricity = 0.172 ± 0.04
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| }}
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| {{OrbitboxPlanet
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| | exoplanet = [[Mu Arae d|d]]
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| | mass = >0.5219
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| | period = 310.55 ± 0.83
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| | semimajor = 0.921
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| | eccentricity = 0.0666 ± 0.0122
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| }}
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| {{OrbitboxPlanet
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| | exoplanet = [[Mu Arae b|b]]
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| | mass = >1.676
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| | period = 643.25 ± 0.90
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| | semimajor = 1.497
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| | eccentricity = 0.128 ± 0.017
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| }}
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| {{OrbitboxPlanet
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| | exoplanet = [[Mu Arae e|e]]
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| | mass = >1.814
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| | period = 4205.8 ± 758.9
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| | semimajor = 5.235
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| | eccentricity = 0.0985 ± 0.0627
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| }}
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| {{Orbitbox end}}
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| [[File:Mu Arae system.jpg|thumb|The Mu Arae star with distance relationships for its four planets]]
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| == See also ==
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| * [[55 Cancri]]
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| * [[Extrasolar planet]]
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| * [[List of extrasolar planets]]
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| * [[PSR 1257+12]]
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| == Notes ==
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| <references group="note" />
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| == References ==
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| {{Reflist|refs=
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| <ref name=aaa474_2_653>{{citation | last1=van Leeuwen | first1=F. | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 |date=November 2007 | pages=653–664 | doi=10.1051/0004-6361:20078357 | bibcode=2007A&A...474..653V | arxiv=0708.1752 }}</ref>
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| <ref name=aj132_1_161>{{citation | display-authors=1 | last1=Gray | first1=R. O. | first2=C. J. | last2=Corbally | first3=R. F. | last3=Garrison | first4=M. T. | last4=McFadden | first5=P. E. | last5=Robinson | 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>
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| <ref name=ibsh8_30>{{citation | 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>
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| <ref name=scfs>{{citation | display-authors=1 | title=Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions | 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 | year=1999 | bibcode=1999VeARI..35....1W }}</ref>
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| <ref name="McCarthy2004">{{cite journal | url=http://iopscience.iop.org/0004-637X/617/1/575/fulltext/ | 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>
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| <ref name=mnras405_3_1907>{{citation | 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. | 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> | |
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| }}
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| == External links ==
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| * [http://webviz.u-strasbg.fr/viz-bin/VizieR-S?GJ%20691 GJ 691]
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| * [http://webviz.u-strasbg.fr/viz-bin/VizieR-S?HR%206585 HR 6585]
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| * {{cite web |url=http://www.space.com/scienceastronomy/super_earth_040825.html |title='Super Earth' Discovered at Nearby Star |accessdate=2008-07-17 |work=[[Space.com]] |publisher= |date=2004-08-25 |first=Robert Roy |last=Britt }}
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| * {{cite web |url=http://www.eso.org/public/outreach/press-rel/pr-2004/pr-22-04.html |title=Fourteen Times the Earth |accessdate=2008-07-17 |work=[[European Southern Observatory]] |publisher= |date=2004-08-25 }}
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| * {{cite web |url=http://obswww.unige.ch/Exoplanets/hd160691.html |title=Mu Ara: a system with 4 planets |accessdate=2008-07-17 |work=Geneva Observatory |publisher= |date= }}
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| * {{cite web |url=http://www.solstation.com/stars2/mu-arae.htm |title=Mu Arae |accessdate=2008-07-17 |work=SolStation |publisher= |date= }}
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| * {{cite web |url=http://www.extrasolar.net/startour.asp?StarCatId=&StarId=128 |title=Mu Arae |accessdate=2008-07-17 |work=Extrasolar Visions |publisher= |date= }}
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| * [http://aladin.u-strasbg.fr/AladinPreview?-c=17+44+08.7029-51+50+02.591&ident=LTT++7053&submit=Aladin+previewer Image Mu Arae]
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| * [http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ Extrasolar Planet Interactions] by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona
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| {{clear}}
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| {{Mu Arae|state=collapsed}}
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| {{Nearest bright star systems|5.}}
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| {{Stars of Ara}}
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| {{Sky|17|44|08.7|-|51|50|03|49.8}}
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| {{Good article}}
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| [[Category:Ara (constellation)]]
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| [[Category:Bayer objects|Arae, Mu]]
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| [[Category:Durchmusterung objects|CD-51 11094]]
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| [[Category:G-type main-sequence stars]]
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| [[Category:G-type subgiants]]
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| [[Category:Gliese and GJ objects|0691]]
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| [[Category:Henry Draper Catalogue objects|160691]]
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| [[Category:Hipparcos objects|086796]]
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| [[Category:HR objects|6585]]
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| [[Category:Planetary systems with four confirmed planets]]
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| [[Category:Objects within 100 ly of Earth]]
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| {{Link GA|cs}}
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