Editing Mu Arae (section)

=== 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 name=Baraffe_et_al_2006/> 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 name=Agnew_et_al_2019/><ref name="Benedict2022"/> 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"/> A 2022 study finds a stable orbital fit to the system, and estimates a lower limit on the system [[orbital inclination|inclination]] of about 20°.<ref name="Goździewski2022"/>

[[Astrometry|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 {{Jupiter mass|<4.3|link=y}}, planet d is {{Jupiter mass|<7.0}}, and planet e is {{Jupiter mass|<4.4}}.<ref name="Benedict2022"/> 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 name=Schütz_et_al_2004/>

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 [[Habitable exomoon|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.<ref name=Canup_Ward_2006/> 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"/> Planet "d" would receive a similar amount of ultraviolet to the Earth and thus lies in the [[Circumstellar_habitable_zone#Spectral_types_and_star-system_characteristics|ultraviolet habitable zone]]. However, it would be too hot for any moons to support surface liquid water.

{{OrbitboxPlanet begin
| table_ref = <ref name="Goździewski2022"/>
}}
{{OrbitboxPlanet
| exoplanet = [[Mu Arae c|c (Dulcinea)]]
| mass = {{val|0.032|0.002|p=≥}}
| period = {{val|9.638|0.001}}
| semimajor = {{val|0.092319|0.000005}}
| eccentricity = {{val|0.090|0.042}}
}}
{{OrbitboxPlanet
| exoplanet = [[Mu Arae d|d (Rocinante)]]
| mass = {{val|0.448|0.011|p=≥}}
| period = {{val|308.36|0.29}}
| semimajor = {{val|0.9347|0.0015}}
| eccentricity = {{val|0.055|0.014}}
}}
{{OrbitboxPlanet
| exoplanet = [[Mu Arae b|b (Quijote)]]
| mass = {{val|1.65|0.009|p=≥}}
| period = {{val|644.92|0.29}}
| semimajor = {{val|1.522|0.001}}
| eccentricity = {{val|0.041|0.009}}
}}
{{OrbitboxPlanet
| exoplanet = [[Mu Arae e|e (Sancho)]]
| mass = {{val|1.932|0.022|p=≥}}
| period = {{val|4019|24|fmt=commas}}
| semimajor = {{val|5.204|0.021}}
| eccentricity = {{val|0.049|0.011}}
}}
{{Orbitbox end}}