Mu Arae

Coordinates: Sky map 17h 44m 08.7s, −51° 50′ 03″
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Mu Arae / Cervantes
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ara
Right ascension 17h 44m 08.70314s[1]
Declination −51° 50′ 02.5916″[1]
Apparent magnitude (V) 5.15[2]
Characteristics
Spectral type G3IV–V[3]
Apparent magnitude (V) 5.15±0.01[2]
Apparent magnitude (G) 4.943±0.003[1]
Apparent magnitude (K) 3.68±0.25[2]
U−B color index +0.24[4]
B−V color index +0.70[4]
Distance
50.89 ± 0.07 ly
(15.60 ± 0.02 pc)
Absolute magnitude (MV)+4.17[5]
Details
Gyr
SAO
 244981
Database references
Exoplanet Archive
data
ARICNSdata

Mu Arae (μ Arae, abbreviated Mu Ara, μ Ara), often designated HD 160691, officially named Cervantes

G-type star approximately 50 light-years away from the Sun in the constellation of Ara. The star has a planetary system with four known extrasolar planets (designated Mu Arae b, c, d and 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 (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 Roman letters starting from "b", in order of discovery.[8] This system was used by a team led by Krzysztof Goździewski.[9] 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.[10] 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,[11] the issue of which convention is 'correct' remains open, however most 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.[12][13]

In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.[14] The process involved public nomination and voting for the new names.[15] 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).[16][17]

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 El Ingenioso Hidalgo Don Quixote de la Mancha. The planets are named after characters of that novel: Quijote was the lead character; Dulcinea his love interest; Rocinante his horse, and Sancho his squire.[18]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[19] to catalog and standardize proper names for stars. In its first bulletin of July 2016,[20] 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.[7]

Stellar characteristics

According to measurements made by the

milliarcseconds 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 50.89 light-years (15.60 parsecs).[1][note 2] Seen from Earth it has an apparent magnitude of +5.15 and is thus visible to the naked eye
.

metal-rich. Mu Arae is also more enriched than the Sun in the element helium.[6]

Mu Arae has a listed

luminosity class, between IV (the subgiants) and V (main sequence dwarf star
stars like the Sun).

Planetary system

Emulation in Celestia of the exoplanets of Cervantes based in the Sudarsky's gas giant classification: Dulcinea, Rocinante, Quijote y Sancho.
The Mu Arae star with distance relationships for its four planets
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

spectrograph.[23]

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.[9][10] 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 core of a gas giant which has had its outer layers stripped away by stellar radiation.[24] Alternatively it may have formed in the inner regions of the Mu Arae system as a rocky "super-Earth".[23]

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:[25][2] 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.[10] A 2022 study finds a stable orbital fit to the system, and estimates a lower limit on the system inclination of about 20°.[26]

Astrometric observations using the Hubble Space Telescope have not detected any of the known planets, but have set upper limits on the masses of the outer three planets: planet b is <4.3 MJ, planet d is <7.0 MJ, and planet e is <4.4 MJ.[2] Searches for circumstellar discs 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.[27]

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

ultraviolet habitable zone
. However, it would be too hot for any moons to support surface liquid water.

The Mu Arae planetary system[26]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
c (Dulcinea) ≥0.032±0.002 MJ 0.092319±0.000005 9.638±0.001 0.090±0.042 — —
d (Rocinante) ≥0.448±0.011 MJ 0.9347±0.0015 308.36±0.29 0.055±0.014 — —
b (Quijote) ≥1.65±0.009 MJ 1.522±0.001 644.92±0.29 0.041±0.009 — —
e (Sancho) ≥1.932±0.022 MJ 5.204±0.021 4,019±24 0.049±0.011 — —

See also

Notes

  1. ^ From [Fe/H] = 0.30 ± 0.01
  2. ^ The formula for converting parallax to distance is

References

  1. ^
    S2CID 244398875
    . Gaia DR3 record for this source at VizieR.
  2. ^
    S2CID 248476290
    .
  3. ^
    S2CID 119476992
    .
  4. ^
    Bibcode:1966IBSH....8...30F
    .
  5. S2CID 119257644
    .
  6. ^
    S2CID 5688996
    .
  7. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016.
  8. arXiv:1012.0707 [astro-ph.SR
    ].
  9. ^
    S2CID 16620036
    .
  10. ^
    S2CID 119071803
    .
  11. ^ "Planets Around Other Stars". IAU. Archived from the original on 28 September 2006. Retrieved 16 September 2006.
  12. S2CID 15410895
    .
  13. ^ "Notes for star HD 160691". Extrasolar Planets Encyclopaedia. Archived from the original on 22 December 2008. Retrieved 11 April 2009.
  14. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
  15. ^ "NameExoWorlds The Process". Archived from the original on 15 August 2015. Retrieved 5 September 2015.
  16. ^ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
  17. ^ "The Proposals page for Mu Arae". International Astronomical Union. 3 January 2016. Archived from the original on 17 April 2019.
  18. ^ NameExoWorlds The Approved Names
  19. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  20. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  21. S2CID 122572834
    .
  22. S2CID 119446133
    .
  23. ^
    S2CID 14938593
    .
  24. S2CID 15574680
    .
  25. doi:10.1093/mnras/stz345
    .
  26. ^
    doi:10.1093/mnras/stac2584
    .
  27. S2CID 25921357
    .
  28. S2CID 4327454
    .
  29. S2CID 2241081
    .

External links

Wikimedia Commons has media related to Mu Arae.


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