Му Арае жұлдызы және оның планеталары

Star in the constellation Ara

Starbox observe
| epoch = J2000.0
| constell = Ara
| ra =
| metal = 200
| metal fe = 0.30 is a main sequence 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.

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. This system was used by a team led by Krzysztof Goździewski. 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. In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. 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). 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. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. In its first bulletin of July 2016, 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. Seen from Earth it has an apparent magnitude of +5.15 and is thus visible to the naked eye. 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. The discovery was made by analysing variations in the star's radial velocity (measured by observing the Doppler shift of the star's spectral lines) 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. 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. 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.

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. Alternatively it may have formed in the inner regions of the Mu Arae system as a rocky "super Earth". 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 moons of the gas giant could potentially support liquid water. On the other hand, it is unclear whether moons sufficiently massive to retain an atmosphere and liquid water could actually form around a gas giant planet, due to a theorized scaling law between the mass of a planet and its satellite system. In addition, measurements of the star's ultraviolet flux suggest that any potentially habitable planets or moons may not receive enough ultraviolet to trigger the formation of biomolecules. 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.