Alpha Centauri A^[1]/B^[2]

The position of Alpha Centauri.
Observation data Epoch J2000
Constellation (pronunciation)	Centaurus
Right ascension	14h 39m 36. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Each culture has its own Constellations usually based on Mythology. Centaurus ( Centaur) is a bright constellation of the southern hemisphere. Right ascension (abbrev RA; symbol α) is the Astronomical term for one of the two Coordinates of a point on the Celestial sphere 4951/35. 0803s
Declination	-60° 50′ 02. In Astronomy, declination (abbrev dec or δ) is one of the two coordinates of the Equatorial coordinate system, the other being either 308/13. 761″
Apparent magnitude (V)	-0. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 01/+1. 33
Characteristics
Spectral type	G2V/K2IV
U-B color index	+0. In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral 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 23/+0. 63
B-V color index	+0. 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 69/+0. 90
Variable type	None
Astrometry
Radial velocity (Rv)	-21. For the astronomical object see Variable star. Variable Star is a 2006 novel written by Spider Robinson Astrometry is the branch of Astronomy that relates to precise measurements and explanations of the positions and movements of Stars and other celestial bodies Radial velocity is the Velocity of an object in the direction of the line of sight (i 6 km/s
Proper motion (μ)	RA: -3678. The proper motion of a Star is the measurement of its change in position in the sky over time after Improper motions are accounted for 19 mas/yr Dec. A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun : 481. 84 mas/yr
Parallax (π)	747. A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between 23 ± 1. 17 mas
Distance	4. A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree. Distance is a numerical description of how far apart objects are 365 ± 0. 007 ly (1. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by 338 ± 0. 002 pc)
Absolute magnitude (MV)	4. History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 In Astronomy, absolute magnitude (also known as absolute visual magnitude) is the Apparent magnitude an object would have if it were at a standard 38/5. 71
Details
Mass	1. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object 100/0. 907[3] M☉
Radius	1. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. Remote Authentication Dial In User Service ( RADIUS) is a networking protocol that provides centralized access authorization and accounting management for people or computers 227/0. 865[3] R☉
Surface gravity (log g)	4. In Astronomy, the solar radius is a unit of Length used to express the size of Stars It is equal to the current radius of the Sun. The surface gravity, g, of an astronomical or other object is the Gravitational acceleration experienced at its surface 30/4. 37[4]
Luminosity	1. Luminosity has different meanings in several different fields of science 519/0. 500[3] L☉
Temperature	5,790/5,260[3] K
Metallicity	151/160%[3] Sun
Age	4. The solar luminosity, L_\odot is a unit of Luminosity ( power emitted in the form of Photons conventionally used by Astronomers to Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic In Astronomy and Physical cosmology, the metallicity of an object is the proportion of its matter made up of Chemical elements other than Hydrogen A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth 85×109[3] years
Visual binary orbit[5]
Companion	Alpha Centauri B
Period (P)	79. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun A binary star is a Star system consisting of two Stars orbiting around their Center of mass. The orbital period is the time taken for a given object to make one complete Orbit about another object 9 yr
Semimajor axis (a)	17. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun In Geometry, the semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae 59"
Eccentricity (e)	0. In Astrodynamics, under standard assumptions, any Orbit must be of Conic section shape 519
Inclination (i)	79. Inclination in general is the Angle between a Reference plane and another plane or axis of direction 23°
Longitude of the node (Ω)	204. The longitude of the ascending node (☊ or Ω is one of the Orbital elements used to specify the Orbit of an object in space 82°
Periastron epoch (T)	1955. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. 59
Argument of periastron (ω)	231. The argument of periapsis (or argument of perifocus) ( ω) is the Orbital element describing the Angle of an Orbiting body's periapsis 80°
Database references
SIMBAD	data
ARICNS	data
Other designations
Rigil Kentaurus, Rigil Kent, Toliman, Bungula, FK5 538, CP(D)−60°5483, GC 19728, CCDM J14396-6050 α Cen A Gl 559 A, HR 5459, HD 128620, GCTP 3309. For the missile mounting see Mistral missile SIMBAD (the S et of I dentifications M easurements and B ibliography for A star catalogue, or star catalog, is an Astronomical catalogue that lists Stars In Astronomy, many stars are referred to simply by catalogue The Catalogue of Fundamental Stars is a series of six astrometric catalogues of high precision positional data for a small selection of stars to define a celestial reference In Astronomy, Durchmusterung or Bonner Durchmusterung ( BD) is the usual name for three comprehensive astrometric Star catalogues A star catalogue, or star catalog, is an Astronomical catalogue that lists Stars In Astronomy, many stars are referred to simply by catalogue The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars or Yale Bright Star Catalogue, is a Star catalogue that lists of all stars of The Henry Draper Catalogue ( HD) is an Astronomical Star catalogue published between 1918 and 1924 giving Spectroscopic classifications A star catalogue, or star catalog, is an Astronomical catalogue that lists Stars In Astronomy, many stars are referred to simply by catalogue 00, LHS 50, SAO 252838, HIP 71683 α Cen B Gl 559 B, HR 5460, HD 128621, LHS 51, HIP 71681 Proxima Cen LHS 49, HIP 70890

Alpha Centauri / α Centauri / α Cen, also known as Rigil Kentaurus or just Rigel Kent, is the brightest star system in the southern constellation of Centaurus. A star catalogue, or star catalog, is an Astronomical catalogue that lists Stars In Astronomy, many stars are referred to simply by catalogue The Smithsonian Astrophysical Observatory Star Catalog is an astrometric Star catalogue. The Hipparcos and Tycho Catalogues (Tycho-1 are the primary products of the European Space Agency 's astrometric mission Hipparcos. A star catalogue, or star catalog, is an Astronomical catalogue that lists Stars In Astronomy, many stars are referred to simply by catalogue The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars or Yale Bright Star Catalogue, is a Star catalogue that lists of all stars of The Henry Draper Catalogue ( HD) is an Astronomical Star catalogue published between 1918 and 1924 giving Spectroscopic classifications A star catalogue, or star catalog, is an Astronomical catalogue that lists Stars In Astronomy, many stars are referred to simply by catalogue The Hipparcos and Tycho Catalogues (Tycho-1 are the primary products of the European Space Agency 's astrometric mission Hipparcos. A star catalogue, or star catalog, is an Astronomical catalogue that lists Stars In Astronomy, many stars are referred to simply by catalogue The Hipparcos and Tycho Catalogues (Tycho-1 are the primary products of the European Space Agency 's astrometric mission Hipparcos. A star system or stellar system is a small number of Stars which orbit each other bound by gravitational attraction. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Centaurus ( Centaur) is a bright constellation of the southern hemisphere. It appears to the naked eye as the third brightest star in the entire night sky, being only outshone by Sirius and Canopus. Sirius is the brightest star in the night sky with a visual Apparent magnitude of &minus1 By total visual magnitude Alpha Centauri AB (α Cen AB) is −0. 27, which shines just fractionally brighter than the fourth brightest individual star in the night sky, Arcturus. |- bgcolor="#FFFAFA"| note (category variability || H and K emission vary In the Southern Hemisphere Rigel Kent is known as the outermost "pointer" to the Southern Cross, but it is too far south to be easily visible for most northern hemisphere observers. CRUX is a lightweight I686 -optimized Linux distribution targeted at experienced Linux users The other, inner "pointer" is Beta Centauri or Agena / Hadar. Beta Centauri (β Cen / β Centauri also known as Hadar or Agena, is the second brightest star in the Constellation Centaurus and the This star lies some 4. 4^o further west of Alpha Centauri, in between the Southern Cross and α Centauri itself. CRUX is a lightweight I686 -optimized Linux distribution targeted at experienced Linux users

Alpha Centauri has the distinction of being the closest of all the stars visible to the naked eye in the night sky. Its distance is about 4. 37 or 4. 4 light years or 1. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by 3 parsecs . History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838

Nature of Alpha Centauri

Alpha Centauri is a gravitational system consisting of three different stars. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth The brightest two stars make a close orbiting binary star, with an additional third distant and fainter component, called Proxima Centauri, Proxima or α Cen C. A binary star is a Star system consisting of two Stars orbiting around their Center of mass. Proxima Centauri ( Latin la ''proximus proxima proximum'' meaning 'next to' or 'nearest to' is a Red dwarf Star approximately 4 Comparing the two brightest individual stars, they rate, respectively, as the fourth and twenty-first brightest stars in the sky - if we exclude the Sun. Bright stars are bright because they have high luminosities and/or they are nearby

Observationally, α Centauri AB remains too close to be resolved by the naked-eye, but for more than two centuries, it has been very well observed and measured by telescopes as small as 5cm in aperture. This presently well established eighty-odd year orbit is therefore of very good accuracy.

Its duplicity, according to the renowned double star observer Robert Aitken (1961), and as now stated in the 6th Catalog of Binary Stars (2008), was originally discovered in December 1689 by Father Richaud from the city of Pondicherry in India while he was observing a comet. Robert Grant Aitken ( December 31 1864 &ndash October 29 1951) was an American Astronomer. Puducherry (formerly; புதுச்சேரி or பாண்டிச்சேரி పాండిచెర్రి പുതുശ്ശേരി Pondichéry is a Proxima Centauri was later discovered by R. T. A. Innes in 1915 from South Africa, being detected by blinking two separate photographic plates taken at different times during one of his dedicated proper motion surveys. The proper motion of a Star is the measurement of its change in position in the sky over time after Improper motions are accounted for Proxima Centauri, like α Centauri AB, showed very large proper motions of both similar size and direction, and this immediately suggested they were likely associated as one system. Distance for Proxima was then later revealed by its tiny but highly significant annual circular movements against the background stars in the star's position - the so-called trigonometric parallax. Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between

Alpha Centauri is now famously known the world over as the closest star system to our Solar System at about 4. The Solar System consists of the Sun and those celestial objects bound to it by Gravity. 37 light-years distant (about 41. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by 5 trillion kilometres, 25. 8 trillion miles or 277,600 AU). This original fact was discovered by Thomas Henderson who had made many stellar observations of both stars in the AB system. Thomas James Henderson ( 28 December 1798 &ndash 23 November 1844) was a Scottish astronomer noted for being the first person to measure He measured accurately the trigonometric parallaxes of both stars between April 1832 and May 1833, but did not formally published them because he seriously doubted his own results - seemingly far too large to be true. Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between Henderson eventually formally published these in 1839, only after Friedrich Wilhelm Bessel had released his own accurate parallax results for the star 61 Cygni in 1838. Friedrich Wilhelm Bessel (22 July 1784 &ndash 17 March 1846 was a German Mathematician, Astronomer, and systematizer of the Bessel functions Not be confused with 16 Cygni, a more distant system containing two G-type stars harboring the Gas giant planet 16 Cygni Bb. Hence, Alpha Centauri is now considered to be the second star to have a calculated distance, even though its present importance is now known as the nearest of all the night time stars.

Proxima Centauri is usually importantly regarded as part of the system, and presently in its orbit is just slightly closer to us than α Centauri AB. Proxima Centauri ( Latin la ''proximus proxima proximum'' meaning 'next to' or 'nearest to' is a Red dwarf Star approximately 4 For this reason Proxima Centauri is celebrated as the closest star to the Sun, lying 4. 22 light-years away. Most of the modern calculated distances for all three stars, as often expressed in the literature, have been derived from the trigonometric parallax placed in the Hipparcos catalog produced in 1991. Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between Hipparcos (an Acronym for Hi gh P recision Par allax Co llecting S atellite) was an Astrometry mission Year 1991 ( MCMXCI) was a Common year starting on Tuesday (link will display full calendar of the Gregorian Calendar.

Alpha Centauri : The Gravitational System

Alpha Centauri is the collective name of a triple star system. It consisting of two main stars, α Cen A and α Cen B, together often labelled as α Cen AB, which is the established binary star system. A binary star is a Star system consisting of two Stars orbiting around their Center of mass. A third component is the much smaller and dimmer red dwarf star named Proxima Centauri or α Cen C. According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool Star, of the Main sequence, either late K Proxima Centauri ( Latin la ''proximus proxima proximum'' meaning 'next to' or 'nearest to' is a Red dwarf Star approximately 4

Size and color of the Sun compared to the stars in the Alpha Centauri system

Alpha Centauri AB

Alpha Centauri A is the principal member or primary of the system and is slightly larger and more luminous than our Sun. The Sun (Sol is the Star at the center of the Solar System. Like the Sun, its similar yellowish-white colour main sequence star that has the stellar classification of a G2 V for its spectral type. The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral characteristics In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral characteristics From the mutual orbital parameters, α Cen A is about 10% more massive than our Sun and the radius has been measured as 23% bigger. ^[3]

Alpha Centauri B is the companion star or secondary to the primary star, and is slightly smaller and dimmer than the Sun. This also main sequence star's spectral type is K1 V, being an observed deeper orangish-yellow colour than the primary star. The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness By mass, α Cen B is about 90% of the Sun, and it is 14. 3% smaller in radius. ^[3] A solar-like rotation period of some 36. 8 days has been determined. ^[6]

Both stars are gravitationally attached, whose orbit is moderately elliptical (e=0. In Astrodynamics, under standard assumptions, any Orbit must be of Conic section shape 5179), ^[7] unlike the planets and the majority of asteroids that orbit our own Sun. They can approach each other in the orbit as close as 11. 2 astronomical units (1. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the 669 billion kilometers or 1. 04 billion miles: roughly the distance from the Sun to Saturn), or receding to 35. 6 AU (5. 9 billion km: being approximately the distance from the Sun to Pluto). The orbital period is 79. 91 years. [1] From this we can easy calculate that the sum of the two masses is about double that of the Sun ([(11. 2 + 35. 6) / 2]³ / 79. 91² = 2. 0, see formula). Small body orbiting a central body Under Standard assumptions in astrodynamics we have m where m \ is the mass These two stars using our knowledge of stellar evolution theory is currently calculated to be slightly older than the Sun. Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime ^[3] The orbit makes the separation and position angle are continuously change, and according to the U.S.N.O.'s 6th Binary Star Catalogue : Ephemeris, the distance between the stars is 8. sEParation is an EP by Destroy Babylon, released on May 4th 2007 Position angle, usually abbreviated PA, is a measurement derived from observing visual binary stars. The United States Naval Observatory ( USNO) is one of the oldest Scientific agencies in the United States. 29 arcsec through P.A. 237^o (2008) and 7. PA (short for Parental Advisory) are a Southern hip hop trio part of the Atlanta -based Dungeon Family. 53 arcsec through P.A. 241 (2009). PA (short for Parental Advisory) are a Southern hip hop trio part of the Atlanta -based Dungeon Family. The next closest approach will be in February 2016, when the distance will reduce to 4. 0 arcsec in PA 300^o. (See External Reference. )

Apparent and real trajectory of B component relative to A component

Proxima Centauri / Alpha Centauri C

Main article: Proxima Centauri

The much fainter red dwarf star named Proxima Centauri, "Proxima", Alpha Centauri C or even "α Cen C", is about 13,000 astronomical units (A. Proxima Centauri ( Latin la ''proximus proxima proximum'' meaning 'next to' or 'nearest to' is a Red dwarf Star approximately 4 According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool Star, of the Main sequence, either late K Proxima Centauri ( Latin la ''proximus proxima proximum'' meaning 'next to' or 'nearest to' is a Red dwarf Star approximately 4 The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the U. ) away from Alpha Centauri AB (1. 94 trillion kilometres, 13,000 A. U. or 0. 21 ly – and about one-twentieth the distance between Alpha Centauri AB and the Sun). A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by It may be in orbit around it, though the period must be in the order of 100,000 to 500,000 years or more. It is possible that the orbit might be hyperbolic, similar to the planetary sling-shot effect adopted by interplanetary spacecraft to change direction and velocity to a second planetary body, and so Proxima may leave the system after a few million years. In Astrodynamics or Celestial mechanics a hyperbolic trajectory is a Kepler orbit with the eccentricity greater than 1 Association with Alpha Centauri AB is unlikely to be entirely accidental, as it shares approximately the same motion through space as the inner binary star system. However, the true gravitational connect remains yet to be proven.

Seen from Earth, Proxima Centauri is separated by 2. 2^o south-west from Alpha Centauri AB. This is about four times the angular diameter of the Full Moon, and almost exact half the distance between Alpha Centauri and Beta Centauri. The angular diameter of an object as seen from a given position is the "visual diameter" of the object measured as an angle A moderate sized telescope is required to see Proxima.

Proxima usually appears as a 13. 1 visual magnitude deep-red star in a poor star field of only several stars. The star is listed in the General Catalogue of Variable Stars (G. The General Catalogue of Variable Stars ( GCVS) is a list of Variable stars. C. V. S. Version 4. 2) as V 645 Cen, being a known UV Ceti-type flare star, which may suddenly and unexpectedly brighten by about two magnitudes or so. Luyten 726-8 is a binary Star system that is one of Earth's nearest neighbors the closest star in the constellation Cetus A flare star is a Variable star which can undergo unpredictable dramatic increases in brightness for a few minutes (11. 0 visual magnitude is often quoted. ) Both amateur and professional have, and continue, to monitor this star from time to time - both visually through optical telescopes and radio telescopes. Proxima is of spectral class M5Ve or M5VIIe, whose B-V colour index is +1. In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral 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 8. As such, the spectral class suggest this is either a small main sequence star (Type V) or sub-dwarf (VII). The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness Its mass is about 0. 4 solar masses. The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies.

The closest stars to the Alpha Centauri system are the Sun and Barnard's star (1. Barnard's Star ( is a very low-mass Red dwarf Star approximately 6 Light-years away in the Constellation of Ophiuchus (the 98 pc or 6. History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 47 ly). From Earth the next nearest star from is 5. 96 ly.

Appearance of the Sky from the Alpha Centauri

Looking toward Sol from Alpha Centauri in Celestia

Viewed from near the Alpha Centauri system, the sky (other than the Alpha Centauri stars) would appear very much as it does to observers on Earth, with most of the constellations such as Ursa Major and Orion being almost unchanged. The Sun (Sol is the Star at the center of the Solar System. Celestia is a 3-D Astronomy program created by Chris Laurel The program is based on the Hipparcos Catalogue (HIP and allows users to travel through an extensive Ursa Major ( is a Constellation visible throughout the year in most of the northern hemisphere Orion (ɒˈraɪən a Constellation often referred to as The Hunter, is a prominent constellation one of the largest and perhaps the best-known and most conspicuous However, Centaurus would be missing its brightest star and our Sun would appear as a 0. The Sun (Sol is the Star at the center of the Solar System. 5-magnitude star in Cassiopeia. Cassiopeia ( colloquially /ˌkæsiˈoʊpiə/ is a northern Constellation which Greek mythology considered to represent the vain queen Cassiopeia who boasted Roughly speaking, the \/\/ of Cassiopeia would become a /\/\/, with the Sun at the end closest to ε Cassiopeiae. Epsilon Cassiopeiae (ε Cas / ε Cassiopeiae is a Star system in the Constellation Cassiopeia. The position can easily be plotted as RA 02h39m35s, Dec. +60°50', or antipodal to Alpha Centauri's position as seen from Earth. Right ascension (abbrev RA; symbol α) is the Astronomical term for one of the two Coordinates of a point on the Celestial sphere In Astronomy, declination (abbrev dec or δ) is one of the two coordinates of the Equatorial coordinate system, the other being either In Mathematics, the antipodal point of a point on the surface of a sphere is the point which is diametrically opposite it — so situated that a line drawn from the

Nearby very bright stars such as Sirius and Procyon would appear to be in very different positions, as would Altair to a lesser extent. Sirius is the brightest star in the night sky with a visual Apparent magnitude of &minus1 This article is about the star Procyon is also the mammalian genus to which raccoons belong Altair (α Aql / α Aquilae / Alpha Aquilae / Atair is the brightest Star in the Constellation Aquila and the twelfth brightest star Sirius would become part of the constellation of Orion, appearing 2 degrees to the west of Betelgeuse, slightly dimmer than from here (-1. Betelgeuse (ˈbiːtəldʒuːz or /ˈbɛtəldʒuːz/ ( α Ori α Orionis Alpha Orionis is a Semiregular variable star located 640 Light-years away from 2). The stars Fomalhaut and Vega, although further away, would appear somewhat displaced as well. Fomalhaut (α PsA / α Piscis Austrini / Alpha Piscis Austrini is the brightest star in the Constellation Piscis Austrinus and one of the brightest Vega (α Lyr / α Lyrae / Alpha Lyrae ( or) is the brightest Star in the Constellation Lyra, the fifth brightest star in the night Proxima Centauri would be an inconspicuous 4. 5 magnitude star, which considering it would only be a quarter of a light-year away shows just how faint Proxima really is. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by

From Proxima, the A–B pair of stars would appear as a very bright star with a combined magnitude of −6. 80. Depending on the position of the binary in their orbit and the eyesight of the observer, the binary pair would appear noticeably double to the naked eye or as one unresolved star. Alpha Centauri A would have an apparent magnitude of −6. 52 and Alpha Centauri B would have an apparent magnitude of −5. 19.

Do Planets Orbit Around Alpha Centauri?

Discovery of additional planets orbiting both single stars and binary star systems, leaves the real possibility of finding either new planets in the Alpha Centauri AB system or planets revolving close to either α Cen A or α Cen B. With additional evidence, like both the principle stars being similar in nature to the Sun, I. e. high metallicity and similar ages, simply reinforces the astronomers view that it is very worthwhile to make detailed searches for planetary bodies around Alpha Centauri. In Astronomy and Physical cosmology, the metallicity of an object is the proportion of its matter made up of Chemical elements other than Hydrogen Additionally, planets have been found in other similar binary systems, such as Gamma Cephei. Gamma Cephei (γ Cep / γ Cephei traditionally named Errai, Er Rai, and or Alrai, is a binary star system approximately 45 Light-years Several established planet-hunting teams have used various radial velocity methods in their searches around these bright stars, but so far all have failed to find any suggestion of any giant gas planets, small terrestrial planets or brown dwarfs. Radial velocity is the Velocity of an object in the direction of the line of sight (i Brown dwarfs are sub- stellar objects with a mass below that necessary to maintain Hydrogen -burning Nuclear fusion reactions in their cores as do stars

Other planetary astronomers consider, based on theoretical computer simulations, that any potential terrestrial planets that did once orbited near the stars' habitable zones are now likely no longer there. The loss of these small bodies may have happened during the system's formation several billion years ago, and all have since been ejected by significant disruptions caused by strong gravitational or perturbation effects generated between the two main stellar components.

In the not too distant future, and if our human technology advances enough to enable voyages for interstellar robotic probes, Alpha Centauri maybe first on the list for exo-planetary exploration. Needless to say, such lengthy trips to cross the huge empty gulfs between the stars would likely still take several centuries, and this still assumes that some interstellar spacecraft could obtain high enough velocities to get there. If present ground or orbit based observatories are unable to detect planets, future exploratory journeys may be the only means of obtaining direct evidence that such planets here do exist.

Alpha Centauri From Hypothetical Planets

A hypothetical planet around either α Centauri A or B would see the other star as a very bright secondary. For example, an Earth-like planet at 1. 25 Astronomical Units from α Cen A (with an orbital period of 1. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the The orbital period is the time taken for a given object to make one complete Orbit about another object 34 a) would get Sun-like illumination from its primary, and α Cen B would appear 5. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun 7 to 8. 6 magnitudes dimmer (−21. 0 to −18. 2), 190 to 2700 times dimmer than α Cen A but still 170 to 2300 times brighter than the full Moon. Conversely, an Earth-like planet at 0. 71 AUs from α Cen B (with thee revolution period of 0. 63 a) would get Sun-like illumination from its primary, and α Cen A would appear 4. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun 6 to 7. 3 magnitudes dimmer (−22. 1 to −19. 4), 70 to 840 times dimmer than α Cen B but still 520 to 6300 times brighter than the full Moon. In both cases the secondary sun would, in the course of the planet's year, appear to circle the sky. Either way, any hypothetical Earthlike planet around either star, the secondary sun would never be bright enough to adversely affect the climate nor significantly affect plant photosynthesis. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy.

If we assume a low orbital inclination of the planet against the orbit of α Cen A and B, the secondary would start beside the primary at stellar conjunction. Half the period later, both stars would be placed opposite of each other in the sky- a 'stellar' opposition. If the distance in the orbit were as far away as Saturn, as similarly view from our Sun, this would mean that for about half the year, the night sky would appear dark blue, instead of being pitch black. The Sun (Sol is the Star at the center of the Solar System. At this time people could easily walk around and see the surrounding terrain with ease, and even reading a book would be possible without any artificial light. After another half period in the orbit, the stars would complete the cycle and return to conjunction. At this time the normal day and night cycle would return.

Possibilities In Planet Formation

Some computer models of planetary formation predict terrestrial planets around both Alpha Centauri A and B^[8][9][10], but suggest that gas giant planets similar to our Jupiter and Saturn would not be able to form because of the binary stars' gravitational effects. A terrestrial planet, telluric planet or rocky planet is a Planet that is primarily composed of Silicate rocks Within our A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large Planet that is not primarily ^[11] Given the similarities in star type, age and stability of the orbits it has been suggested that this stellar system may hold one of the best possibilities for extraterrestrial life. Extraterrestrial life is Life originating outside of the Earth. ^[12] However, some astronomers have speculated that any terrestrial planets in the Alpha Centauri system may be dry because it is believed that Jupiter and Saturn were crucial at directing comets into the inner solar system and providing the inner planets with a source of water. A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — Water is a common Chemical substance that is essential for the survival of all known forms of Life. This would not be a problem, however, if Alpha Centauri B happened to play a similar role for Alpha Centauri A that the gas giants do for the Sun, and vice versa. The Sun (Sol is the Star at the center of the Solar System. Both stars are of the right spectral type to possibly harbour life on some potential planet. In Astronomy, stellar classification is a classification of Stars based initially on photospheric temperature and its associated Spectral characteristics ^[13][14][15]

Any suspected planet around Alpha Centauri A would be about 1. 25 AU away from the star if it were to have Earthlike temperatures, or about halfway between the distances of Earth's orbit and Mars' orbit in our own solar system. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The Solar System consists of the Sun and those celestial objects bound to it by Gravity. For dimmer, cooler Alpha Centauri B, the distance would be about 0. 7 AU, or about the distance of Venus from the Sun. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University The Sun (Sol is the Star at the center of the Solar System.

Proxima Centauri, along with Alpha Centauri A and B, are among the "Tier 1" target stars for NASA's Space Interferometry Mission (SIM). The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The Space Interferometry Mission, also known as SIM PlanetQuest, is a planned space telescope being developed by the U SIM is designed to be able to detect planets as small as three Earth-masses or smaller within two Astronomical Units of a "Tier 1" target. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the ^[16]

Apparent Movement by Proper Motion

Apparent motion of Alpha Centauri relative to Beta Centauri. Beta Centauri (β Cen / β Centauri also known as Hadar or Agena, is the second brightest star in the Constellation Centaurus and the

Around 5973 C.E, the significantly large proper motion of Alpha Centauri will lead to a situation where some earthbound observer would see a naked-eye visual double star adjoined with the slightly fainter 1st magnitude star Beta Centauri only 23 arcmin apart. The proper motion of a Star is the measurement of its change in position in the sky over time after Improper motions are accounted for Double Star is a Science fiction Novel by Robert A Heinlein, first serialized in Astounding Science Fiction Beta Centauri (β Cen / β Centauri also known as Hadar or Agena, is the second brightest star in the Constellation Centaurus and the A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree. This spectacular duo will form an example of a very rare stellar conjunction. In reality, Beta Centauri is just over 120 times more distant than Alpha Centauri, (530 to 4. Beta Centauri (β Cen / β Centauri also known as Hadar or Agena, is the second brightest star in the Constellation Centaurus and the 3 light-years), passing each other like ships in the night. ^[17]

After this, Alpha Centauri will continue to slowly brighten, passing north of the Southern Cross or Crux, before moving in a northwest direction towards the celestial equator and away from the galactic plane. CRUX is a lightweight I686 -optimized Linux distribution targeted at experienced Linux users CRUX is a lightweight I686 -optimized Linux distribution targeted at experienced Linux users The celestial equator is a Great circle on the imaginary Celestial sphere, in the same plane as the Earth 's Equator. The galactic coordinate system is a Celestial coordinate system which is centered on the Sun and is aligned with the apparent center of the Milky Way galaxy By 29,700 C.E, α Centauri will lie exactly 1. 00 parsecs or 3. History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 26 light-years, and will reach its maximum brightness of -0. 86 magnitude - similar in brightness to present day Canopus. At this time it will be placed near the present-day constellation of Hydra. HYDRA is a fictional terrorist organization in the Marvel Universe. Soon after this relatively close solar approach, the system will then begin moving away from the Sun. In 43,300 AD, α Centauri will pass near 2nd magnitude Alpha Hydrae / Alphard. For the programming language see Alphard (programming language. For the programming language see Alphard (programming language. The visual magnitude at this time will be +1. 03 and the distance will be 5. 36 ly. ^[18]

The final fixed merge point will occur more than 100,000 years hence, where this once dominant bright star will finally disappear below naked-eye visibility somewhere in present day faint southern constellation of Telescopium. Telescopium (ˌtɛlɪˈskɒpiəm is a minor southern Constellation identified by Nicolas Louis de Lacaille, the 18th century French Astronomer This unusual location is easily explained because α Centauri has a galactic orbital motion that happens to be highly tilted in respect of our Milky Way galaxy. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply

Origin of Name and Cultural Significance

The system bears the proper name Rigil Kentaurus^[19] (often shortened to Rigil Kent. ^[20], former Rigjl Kentaurus^[21][22], and Riguel Kentaurus^[23] in Portuguese), derived from the Arabic phrase Rijl Qantūris^[20] (meaning "Foot of the Centaur)," but is most often referred to by its Bayer designation Alpha Centauri. Portuguese ( or língua portuguesa) is a Romance language that originated in what is now Galicia (Spain and northern Portugal. Arabic (ar الْعَرَبيّة (informally ar عَرَبيْ) in terms of the number of speakers is the largest living member of the Semitic language Centaurus ( Centaur) is a bright constellation of the southern hemisphere. A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's An alternative name is Toliman, whose etymology may be Arabic al-Zulmān (meaning "the Ostriches"), or Hebrew (meaning "The Heretofore and the Hereafter" and/or "Shoot of the Vine"). (See Centaurus) Finally, it is sometimes called Bungula^[24], possibly coined from "β" and the Latin ungula (meaning "hoof"). Centaurus ( Centaur) is a bright constellation of the southern hemisphere. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. This latter name in modern times is, however, rarely used.

In Chinese, Alpha Centauri was called Nánmén'èr (南門二) "Second Star of the Southern Gate". As mentioned, Alpha and Beta Centauri together form the "Southern Pointers" to Crux, the Southern Cross. CRUX is a lightweight I686 -optimized Linux distribution targeted at experienced Linux users

Alpha Centauri in Modern Fiction

Main article: Alpha Centauri in fiction

Alpha Centauri's relative proximity makes it a in some ways likely the logical choice as "first port of call". Alpha Centauri, the closest Star system to the Sun, is frequently referenced in Science fiction stories especially those involving Interstellar Speculative fiction about interstellar travel predicts eventual human exploration, and even the discovery and colonization of planetary systems. Speculative fiction is a term used as an inclusive descriptor covering a group of Fiction Genres that speculate about worlds that are unlike the real world in Interstellar space travel is unmanned or manned Travel between Stars The concept of interstellar travel in Starships is a staple in Science fiction History First orbital flights The first successful orbital launch was of the Soviet unmanned Sputnik For the compulsory pre-trial disclosure of documents relevant to a case see Discovery (law Discovery Observations form acts of detecting Space colonization (also called space settlement, space humanization, Space habitation, etc These themes are common to many works of science fiction and video games. A video game is a Game that involves interaction with a User interface to generate visual feedback on a video device. Because of its status as our nearest galactic neighbor, Alpha Centauri has frequently been referred to in science fiction stories involving interstellar travel. Interstellar space travel is unmanned or manned Travel between Stars The concept of interstellar travel in Starships is a staple in Science fiction

References

External links

• SIMBAD observational data
• Sixth Catalogue of Orbits of Visual Binary Stars U.S.N.O.
• Sixth Catalogue of Orbits of Visual Binary Stars : Orbital Elements U.S.N.O.
• Sixth Catalogue of Orbits of Visual Binary Stars : Orbit Notes U.S.N.O.
• Sixth Catalogue of Orbits of Visual Binary Stars : Orbit Notes U.S.N.O.
• The Imperial Star - Alpha Centauri
• Alpha Centauri - A Voyage to Alpha Centauri
• Immediate History of Alpha Centauri
• eSky : Alpha Centauri

References on Hypothetical Planets or Exploration

• A Family Portrait of the Alpha Centauri System. SpaceRef. com. Retrieved on 21 March, 2003.
• Alpha Centauri article at Memory Alpha, a Star Trek wiki
• Alpha Centauri System
• O Sistema Alpha Centauri (portuguese)
• Alpha Centauri - Associação de Astronomia (portuguese)
• http://www.space.com/scienceastronomy/080307-another-earth.html

See Also

• List of nearest stars
• List of brightest stars
• Project Longshot