HOME

TheInfoList



OR:

Mu Arae (μ Arae, abbreviated Mu Ara, μ Ara), often designated HD 160691, officially named Cervantes , is a
main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...
G-type
star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
approximately 50
light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s away from the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...
of
Ara ARA may refer to: Media and the arts * American-Romanian Academy of Arts and Sciences * '' Artistička Radna Akcija'', compilation album released in former Yugoslavia * Associate of the Royal Academy, denoting membership in the British Royal Aca ...
. The star has a
planetary system A planetary system is a set of gravitationally In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interacti ...
with four known
extrasolar planets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
(designated
Mu Arae b Mu Arae b, often designated HD 160691 b, formally named Quijote , is an exoplanet orbiting the star Mu Arae of the constellation Ara (constellation), Ara. The planet is at least one and a half times the mass of Jupiter, and its orbital period is ...
, c, d and e; later named Quijote, Dulcinea, Rocinante and Sancho, respectively), three of them with masses comparable with that of
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...
. Mu Arae c, the innermost, was the first
hot Neptune A hot Neptune or Hoptune is a type of giant planet with a mass similar to that of Uranus or Neptune orbiting close to its star, normally within less than 1 AU. The first hot Neptune to be discovered with certainty was Gliese 436 b in 2007, an exo ...
or
super-Earth A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to ...
discovered.


Nomenclature

''μ Arae'' ( Latinised to ''Mu Arae'') is the star's
Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. ...
. 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 The Latin script, also known as Roman script, is an alphabetic writing system based on the letters of the classical Latin alphabet, derived from a form of the Greek alphabet which was in use in the ancient Greece, Greek city of Cumae, in southe ...
starting from "b", in order of discovery. This system was used by a team led by
Krzysztof Goździewski Krzysztof () is a Polish given name, equivalent to English ''Christopher''. The name became popular in the 15th century. Its diminutive forms include Krzyś, Krzysiek, and Krzysio; augmentative – Krzychu Individuals named Krzysztof may choose to ...
. On the other hand, a team led by
Francesco Pepe Francesco, the Italian (and original) version of the personal name "Francis", is the most common given name among males in Italy. Notable persons with that name include: People with the given name Francesco * Francesco I (disambiguation), sever ...
proposed a modification of the designation system, where the planets are designated in order of characterization. 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 The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...
has not defined an official system for designations of extrasolar planets, 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 The Extrasolar Planets Encyclopaedia is an astronomy website, founded in Paris, France at the Meudon Observatory by Jean Schneider in February 1995, which maintains a database of all the currently known and candidate extrasolar planets, with indi ...
. In July 2014 the
International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...
launched
NameExoWorlds NameExoWorlds (also known as IAU NameExoWorlds) is the name of various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, which would later be considered for official ad ...
, 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 Miguel de Cervantes Saavedra (; 29 September 1547 (assumed) – 22 April 1616 Old Style and New Style dates, NS) was an Early Modern Spanish writer widely regarded as the greatest writer in the Spanish language and one of the world's pre-emin ...
Saavedra (1547–1616) was a famous Spanish writer and author of ''
El Ingenioso Hidalgo Don Quixote de la Mancha is a Spanish epic novel by Miguel de Cervantes. Originally published in two parts, in 1605 and 1615, its full title is ''The Ingenious Gentleman Don Quixote of La Mancha'' or, in Spanish, (changing in Part 2 to ). A founding work of Western ...
''. The planets are named after characters of that novel: Quijote was the lead character;
Dulcinea Dulcinea del Toboso is a fictional character who is unseen in Miguel de Cervantes' novel ''Don Quijote''. Don Quijote believes he must have a lady, under the mistaken view that chivalry requires it. As he does not have one, he invents her, mak ...
his love interest;
Rocinante Rocinante () is Don Quixote's horse in the two-part 1605/1615 novel ''Don Quixote'' by Miguel de Cervantes. In many ways, Rocinante is not only Don Quixote's horse, but also his double; like Don Quixote, he is awkward, past his prime, and ...
his horse, and
Sancho The name Sancho is an Iberian name of Basque origin (Santxo, Santzo, Santso, Antzo, Sans). Sancho stems from the Latin name Sanctius.Eichler, Ernst; Hilty, Gerold; Löffler, Heinrich; Steger, Hugo; Zgusta, Ladislav: ''Namenforschung/Name Studies/ ...
his
squire In the Middle Ages, a squire was the shield- or armour-bearer of a knight. Use of the term evolved over time. Initially, a squire served as a knight's apprentice. Later, a village leader or a lord of the manor might come to be known as a " ...
. In 2016, the IAU organized a
Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...
(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.


Stellar characteristics

According to measurements made by the
Gaia In Greek mythology, Gaia (; from Ancient Greek , a poetical form of , 'land' or 'earth'),, , . also spelled Gaea , is the personification of the Earth and one of the Greek primordial deities. Gaia is the ancestral mother—sometimes parthenog ...
astrometric Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. Histor ...
satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
, Mu Arae exhibits a
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
of 64.0853
milliarcsecond A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...
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 .The formula for converting parallax to distance is \scriptstyle\mathrm=\frac Seen from Earth it has an
apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...
of +5.15 and is thus visible to the
naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to normal ...
. 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 Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
of the Sun and is therefore described as
metal-rich In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
. Mu Arae is also more enriched than the Sun in the element
helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
. Mu Arae has a listed
spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...
of G3IV–V. The G3 part means the star is similar to the Sun (a G2V star). The star may be entering the
subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...
stage of its evolution as it starts to run out of
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
in its core. This is reflected in its uncertain
luminosity class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...
, between IV (the subgiants) and V (
main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...
dwarf star A dwarf star is a star of relatively small size and low luminosity. Most main sequence stars are dwarf stars. The meaning of the word "dwarf" was later extended to some star-sized objects that are not stars, and compact stellar remnants which are ...
stars like the Sun).


Planetary system


Discovery

In 2001, an extrasolar planet was announced by the
Anglo-Australian Planet Search The Anglo Australian Planet Search or (AAPS) is a long-term astronomical survey started in 1998 and continuing to the present. It is being carried out on the 3.9-metre Anglo-Australian Telescope (AAT) of the Anglo-Australian Observatory in Austral ...
team, together with the planet orbiting
Epsilon Reticuli Epsilon Reticuli, Latinized from ε Reticuli, is a double star approximately 59 light-years away in the constellation of Reticulum. The primary component is an orange subgiant, while the secondary is a white dwarf. The two sta ...
. The planet, designated
Mu Arae b Mu Arae b, often designated HD 160691 b, formally named Quijote , is an exoplanet orbiting the star Mu Arae of the constellation Ara (constellation), Ara. The planet is at least one and a half times the mass of Jupiter, and its orbital period is ...
, was thought to be in a highly
eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...
orbit of around 743 days. The discovery was made by analysing variations in the star's
radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...
(measured by observing the
Doppler shift The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who d ...
of the star's
spectral line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...
s) as a result of being pulled around by the planet's
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
. Further observations revealed the presence of a second object in the system (now designated as
Mu Arae e Mu Arae e, also known as HD 160691 e, later named Sancho , is one of the four extrasolar planets orbiting the star Mu Arae of the constellation Ara. In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving p ...
), 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. Later in 2004, a small inner planet designated
Mu Arae c Mu Arae c, also known as HD 160691 c, formally named Dulcinea (pronounced or ), is an extrasolar planet orbiting the star Mu Arae of the constellation Ara. It was the first 'hot Neptune' or 'mega-Earth' to be discovered. None of the four planets ...
was announced with a mass comparable with that of
Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus (mythology), Uranus (Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars (mythology), Mars), grandfather ...
in a 9-day orbit. This was the first of the class of planets known as "
hot Neptune A hot Neptune or Hoptune is a type of giant planet with a mass similar to that of Uranus or Neptune orbiting close to its star, normally within less than 1 AU. The first hot Neptune to be discovered with certainty was Gliese 436 b in 2007, an exo ...
s" to be discovered. The discovery was made by making high-precision radial velocity measurements with the
High Accuracy Radial Velocity Planet Searcher The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. H ...
(HARPS)
spectrograph An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...
. In 2006, two teams, one led by
Krzysztof Goździewski Krzysztof () is a Polish given name, equivalent to English ''Christopher''. The name became popular in the 15th century. Its diminutive forms include Krzyś, Krzysiek, and Krzysio; augmentative – Krzychu Individuals named Krzysztof may choose to ...
and the other by
Francesco Pepe Francesco, the Italian (and original) version of the personal name "Francis", is the most common given name among males in Italy. Notable persons with that name include: People with the given name Francesco * Francesco I (disambiguation), sever ...
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 55 Cancri is a binary star system located 41 light-years away from the Sun in the zodiac constellation of Cancer. It has the Bayer designation Rho1 Cancri (ρ1 Cancri); ''55 Cancri'' is the Flamsteed designation (abbrevia ...
.


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 Chthonian planets (, sometimes 'cthonian') are a hypothetical class of celestial objects resulting from the stripping away of a gas giant's hydrogen and helium atmosphere and outer layers, which is called hydrodynamic escape. Such atmospheric ...
, the
core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the central ...
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 inner gas giants "d" and "b" are located close to the 2:1
orbital resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...
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 Gliese 876 is a red dwarf approximately 15 light-years away from Earth in the constellation of Aquarius. It is one of the closest known stars to the Sun confirmed to possess a planetary system with more than two planets, after Gliese ...
system) can be found which give only a slightly worse fit to the data. A 2022 study finds a stable orbital fit to the system, and estimates a lower limit on the system
inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...
of about 20°.
Astrometric Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. Histor ...
observations using the
Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...
have not detected any of the known planets, but have set upper limits on the masses of the outer three planets: planet b is , planet d is , and planet e is . Searches for
circumstellar disc A circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the reser ...
s show no evidence for a debris disc similar to the
Kuiper belt The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...
around Mu Arae. If Mu Arae does have a Kuiper belt, it is too faint to be detected with current instruments. 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 A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''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 Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
suggest that any potentially
habitable Habitability refers to the adequacy of an environment for human living. Where housing is concerned, there are generally local ordinances which define habitability. If a residence complies with those laws it is said to be habitable. In extreme e ...
planets or moons may not receive enough ultraviolet to trigger the formation of
biomolecule A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include large ...
s. 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.


See also

*
55 Cancri 55 Cancri is a binary star system located 41 light-years away from the Sun in the zodiac constellation of Cancer. It has the Bayer designation Rho1 Cancri (ρ1 Cancri); ''55 Cancri'' is the Flamsteed designation (abbrevia ...
*
Exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
*
Lists of exoplanets These are lists of exoplanets. Most of these were discovered by the Kepler space telescope. There are an additional 2,054 potential exoplanets from Kepler's first mission yet to be confirmed, as well as 978 from its "Second Light" mission and 4 ...
*
PSR B1257+12 PSR B1257+12, previously designated PSR 1257+12, alternatively designated PSR J1300+1240, is a millisecond pulsar located 2,300 light-years from the Sun in the constellation of Virgo, rotating at about 161 times per second (faster than a ...


Notes


References


External links


GJ 691

HR 6585
* * * *
Image Mu Arae

Extrasolar Planet Interactions
by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona {{DEFAULTSORT:Mu Arae Ara (constellation) Arae, Mu CD-51 11094 G-type main-sequence stars G-type subgiants 0691 160691 086796 6585 Planetary systems with four confirmed planets