NationMaster - Encyclopedia: Mu Arae

Mu Arae (μ Ara / μ Arae) is a Sunlike yellow-orange star located around 50 light years away in the 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" to be discovered. An image of Mu Arae from NASAs Nstars database. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... It has been suggested that this article or section be merged into Julian epoch. ... This article is about the star grouping. ... From the dawn of time, poop observed the sky and grouped stars into patterns or constellations. ... Ara (Latin for Altar) is a faint southerly constellation between the constellations Centaurus and Lupus. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (abbrev. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. ... In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. ... This article or section contains a plot summary that is overly long or excessively detailed. ... Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ... Radial velocity is the velocity of an object in the direction of the line of sight. ... kilometre per second is an SI derived unit of both speed (scalar) and velocity (vector), signified by the symbol km/s or km s-1. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... For other uses, see Parallax (disambiguation). ... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... Distance is a numerical description of how far apart objects are at any given moment in time. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... For other uses, see Mass (disambiguation). ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... This article is about an authentication, authorization, and accounting protocol. ... In astronomy, the solar radius is a unit of length used to express the size of stars and larger objects such as galaxies. ... This article does not cite any references or sources. ... The solar luminosity, , is a unit of luminosity (power emitted in the form of photons) conventionally used by astronomers to give the luminosities of stars. ... For other uses, see Temperature (disambiguation). ... For other uses, see Kelvin (disambiguation). ... The globular cluster M80. ... This illustration shows the oblate appearance of the star Achernar caused by rapid rotation. ... This article is about the astronomical object. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... A star catalogue, or star catalog, is an astronomical catalog that lists stars. ... In astronomy, many stars are referred to simply by catalogue numbers. ... The Henry Draper Catalogue is an astronomy catalogue with astrometric and spectroscopic data about more than 225,000 stars. ... In astronomy, many stars are referred to simply by catalogue numbers. ... In astronomy, many stars are referred to simply by catalogue numbers. ... Fifth Fundamental Catalogue is a glossary of positions of stars. ... The Hipparcos and Tycho Catalogues (Tycho-1) are the primary products of the European Space Agencys astrometric mission, Hipparcos. ... In astronomy, many stars are referred to simply by catalogue numbers. ... Sol redirects here. ... This article is about the astronomical object. ... This article is about the star grouping. ... Ara (Latin for Altar) is a faint southerly constellation between the constellations Centaurus and Lupus. ... An artists concept of a protoplanetary disc. ... For other uses, see Jupiter (disambiguation). ...

Distance and visibility

According to measurements made by the Hipparcos astrometric satellite, Mu Arae exhibits a parallax of 65.46 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 49.8 light years (15.3 parsecs).^[1] Seen from Earth it has an apparent magnitude of +5.12 and is visible to the naked eye. Hipparcos (for High Precision Parallax Collecting Satellite) was an astrometry mission of the European Space Agency (ESA) dedicated to the measurement of stellar parallax and the proper motions of stars. ... Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ... For other uses, see Satellite (disambiguation). ... For other uses, see Parallax (disambiguation). ... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... This article is about Earth as a planet. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... This article is about Earth as a planet. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... The naked eye is a figure of speech referring to human visual perception that is unaided by enhancing equipment, such as a telescope or binoculars. ...

Stellar characteristics

Mu Arae is estimated to be slightly more massive than our Sun at around 1.10 solar masses. Based on the abundance of iron, it is around twice as enriched in heavy elements as our Sun, and is therefore described as metal-rich. Its surface temperature of around 5800 K is similar to our Sun.^[2] The star has a radius estimated to be 31.5% greater than our Sun and is 75% more luminous.^[3] For other uses, see Mass (disambiguation). ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... For other uses, see Iron (disambiguation). ... In astronomy and cosmology, the term metal or metal-rich is used to refer to any element heavier than hydrogen and helium. ... For other uses, see Temperature (disambiguation). ... For other uses, see Kelvin (disambiguation). ... This article is about an authentication, authorization, and accounting protocol. ... This article does not cite any references or sources. ...

As a star ages, the level of activity in its chromosphere is expected to decline. Based on observed activity levels, the age of Mu Arae is estimated to be around 6,410 million years or 1,450 million years, depending on the theoretical model used.^[4] Another way to estimate the star's age is to match its properties with models of stellar evolution. This method suggests an age of around 4,400 million years.^[3] The chromosphere (literally, color sphere) is a thin layer of the Suns atmosphere just above the photosphere, roughly 10,000 kilometers deep (approximating to, if a little less than, the diameter of the Earth). ... Mega-annum, usually abbreviated as Ma, is a unit of time equal to one million years. ... Projected timeline of the Suns life In astronomy, stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. ...

Mu Arae has a listed spectral type of G3IV–V. The G3 part means the star is classified as yellow in colour, 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 stars like the Sun). In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... Subgiant are Olly Maw, Dan Hayes and Tushar Joshi, a live dance music band from the UK formed in 2000. ... This article is about the chemistry of hydrogen. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ...

Planetary system

As of August 2006, four extrasolar planets have been detected in orbit around Mu Arae. Three have high masses and are likely to be gas giants. The innermost planet has a mass comparable to that of Uranus and may either be a small gas giant or a large terrestrial planet. The other 3 are Jupiter-Sized planets. Image File history File links MuAraeOuterOrbits. ... Image File history File links MuAraeOuterOrbits. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... This article does not cite any references or sources. ... For other uses, see Uranus (disambiguation). ... The inner planets, Mercury, Venus, Earth, and Mars, their sizes to scale. ...

Discovery

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 eccentric orbit of around 743 days.^[5] 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. Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... The Anglo-Australian Observatory (AAO) is an optical astronomy observatory with its headquarters in suburban Sydney, Australia. ... Our inner solar system superimposed behind the orbits of the planets HD 179949 b, HD 164427 b, Epsilon Reticuli ab, and Mu Arae b (each planet has its parent star labeled next to it -- all parent stars are in the center) Epsilon Reticuli (Îµ Ret / Îµ Reticuli) is a 4th magnitude star... Mu Arae b is at least one and a half times the mass of Jupiter and orbits within the stars habitable zone. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... Radial velocity is the velocity of an object in the direction of the line of sight. ... The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ... Gravity is a force of attraction that acts between bodies that have mass. ...

Further observations revealed the presence of a second object in the system (Mu Arae c), 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.^[6] Mu Arae c was announced on June 13, 2002. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ...

Later in 2004, a small inner planet designated Mu Arae d 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 Neptunes" to be discovered. The discovery was made by making high-precision radial velocity measurements with the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph.^[2] Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Mu Arae d at the time of its discovery was the least massive extrasolar planet found around a main sequence star. ... For other uses, see Uranus (disambiguation). ... The High Accuracy Radial velocity Planet Searcher (HARPS) is a high-precision echelle spectrograph installed in 2002 with first light achieved February 2003 on ESOs 3. ... For Acoustic uses in spectrographs of sound waves, see below. ...

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 e) in a near-circular orbit lasting approximately 311 days.^[7]^[8] The new model gives revised parameters for the previously known planets, with lower eccentricity orbits than in the previous model. The discovery of the fourth planet made Mu Arae the second known four-planet extrasolar system, after 55 Cancri. Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Mu Arae e was announced on August, 2006. ... 55 Cancri (abbreviated 55 Cnc; Bayer designation Ï1 Cancri, Rho-1 Cancri) is a nearby 6th magnitude star in the constellation Cancer. ...

System structure

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.^[9] Alternatively it may have formed in the inner regions of the Mu Arae system as a rocky "super-Earth".^[2] A Chthonian planet (sometimes misspelled Cthonian), is a gas giant with its hydrogen and helium atmosphere stripped away due to its closeness to its star. ... The planetary core consists of the innermost layer(s) of a planet. ...

The inner gas giants "e" 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.^[8] In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... Gliese 876 is a red dwarf star located approximately 15 light-years away in the constellation Aquarius. ...

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.^[10] A proplyd in the Orion Nebula. ... The Kuiper belt, derived from data from the Minor Planet Center. ...

For other uses, see Jupiter (disambiguation). ... Look up day in Wiktionary, the free dictionary. ... The astronomical unit (AU or au or a. ... Mu Arae d at the time of its discovery was the least massive extrasolar planet found around a main sequence star. ... Mu Arae e was announced on August, 2006. ... Mu Arae b is at least one and a half times the mass of Jupiter and orbits within the stars habitable zone. ... Mu Arae c was announced on June 13, 2002. ...

Habitability

The gas giant planet "b" is located in the liquid water habitable zone of Mu Arae. This would prevent an Earthlike planet from forming in the habitable zone, however large moons or Trojan planets 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.^[11] 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.^[12] A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ... A trojan planet is a theoretical planet orbiting in the lagrange point of a star and a massive orbiting body, a gas giant or potentially a smaller companion star. ... For other uses, see Ultraviolet (disambiguation). ... flux in science and mathematics. ... Understanding planetary habitability is partly an extrapolation of the Earths conditions, as it is the only planet currently known to support life. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...

Planet "e" 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.

Planet naming conventions

The established convention for extrasolar planets is that the planets receive lower-case Roman letters starting from "b", in order of discovery. This system is used by the team led by Goździewski,^[7] and has been adopted in this article for compatibility with the designations used previously for the 3-planet model. The Latin alphabet, also called the Roman alphabet, is the most widely used alphabetic writing system in the world today. ...

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 characterisation.^[8] 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 670-day planet as "b". The Pepe system designates the 9-day planet as "c", the 310-day planet as "d" and the outer planet as "e".

Since the International Astronomical Union has not defined an official system for designations of extrasolar planets,^[13] the issue of which convention is "correct" remains open. IAU redirects here. ...

References

^ HIP 86796. The Hipparcos and Tycho Catalogues. ESA (1997). Retrieved on 10 September, 2006.
^ ^a ^b ^c Santos et al. (2004). "The HARPS survey for southern extra-solar planets II. A 14 Earth-masses exoplanet around μ Arae". Astronomy and Astrophysics 426: L19 – L23.
^ ^a ^b Valenti, J. et al. (2005). SPOCS 763. Spectroscopic properties of cool stars. I.. Retrieved on 10 September, 2006.
^ Saffe, C. et al. (2005). "On the Ages of Exoplanet Host Stars". Astronomy and Astrophysics 443 (2): 609 – 626.
^ Butler, R. et al. (2001). "Two New Planets from the Anglo-Australian Planet Search". The Astrophysical Journal 555 (1): 410 – 417.
^ McCarthy et al. (2004). "Multiple Companions to HD 154857 and HD 160691". The Astrophysical Journal 617 (1): 575-579.
^ ^a ^b Gozdziewski, K. et al. (2006). "14, 2006 About the extrasolar multi-planet system around HD160691" arxiv:astro-ph/0608279August 14, 2006.
^ ^a ^b ^c Pepe, F. et al. (2006). "18, 2006 The HARPS search for southern extra-solar planets. IX. μ Ara, a system with four planets" arxiv:astro-ph/0608396August 18, 2006.
^ Baraffe, I. et al. (2006). "Birth and fate of hot-Neptune planets". Astronomy and Astrophysics 450 (3): 1221 – 1229.
^ Schütz, O. et al. (2004). "A search for circumstellar dust disks with ADONIS". Astronomy and Astrophysics 424: 613 – 618.
^ Canup, R., Ward, W. (2006). "A common mass scaling for satellite systems of gaseous planets". Nature 441: 834 – 839.
^ Buccino, A. et al. (2006). "Ultraviolet Radiation Constraints around the Circumstellar Habitable Zones". Icarus 183 (2): 491 – 503.
^ Planets Around Other Stars. IAU. Retrieved on 16 September, 2006.

Astronomy and Astrophysics (often referred to as A&A) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ... Astronomy and Astrophysics (often referred to as A&A) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ... The Astrophysical Journal is a scientific journal covering astronomy and astrophysics. ... The Astrophysical Journal is a scientific journal covering astronomy and astrophysics. ... Astronomy and Astrophysics (often referred to as A&A) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ... Astronomy and Astrophysics (often referred to as A&A) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ... Nature is a prominent scientific journal, first published on 4 November 1869. ... ICARUS is the official journal of the Division for Planetary Sciences of the American Astronomical Society. ...

Contents

Distance and visibility

Stellar characteristics

Planetary system

Discovery

System structure

Habitability

Planet naming conventions

References

See also

External links

Contents

Distance and visibility GA_googleFillSlot("encyclopedia_square");

Stellar characteristics

Planetary system

Discovery

System structure

Habitability

Planet naming conventions

References

See also

External links

Distance and visibility