Editing Proxima Centauri (section)

== Motion and location ==
[[File:Angular map of fusors around Sol within 9ly (large).png|thumb|upright=1.2| Proxima Centauri (unlabeled) next to Alpha Centauri on a radar map of all known stellar and [[substellar]] objects within 9 light years (ly), arranged clockwise in [[hour angle|hours]] of [[right ascension]], and  marked by distance (▬) and position (◆)]]

Based on a parallax of {{val|768.0665|0.0499|u=mas}}, published in 2020 in [[Gaia Data Release 3]], Proxima Centauri is {{convert|4.2465|ly|pc AU|lk=on}} from the Sun.<ref name="Gaia3" /> Previously published parallaxes include: {{val|768.5|0.2|u=mas}} in 2018 by Gaia DR2, {{val|768.13|1.04|u=mas}}, in 2014 by the [[Research Consortium On Nearby Stars]];<ref name="lurie2014">{{cite journal |last1=Lurie |first1=John C. |last2=Henry |first2=Todd J. |last3=Jao |first3=Wei-Chun |last4=Quinn |first4=Samuel N. |last5=Winters |first5=Jennifer G. |last6=Ianna |first6=Philip A. |last7=Koerner |first7=David W. |last8=Riedel |first8=Adric R. |last9=Subasavage |first9=John P. |year=2014 |title=The Solar neighborhood. XXXIV. A search for planets orbiting nearby M dwarfs using astrometry |journal=The Astronomical Journal |volume=148 |issue=5 |pages=91 |arxiv=1407.4820 |bibcode=2014AJ....148...91L |doi=10.1088/0004-6256/148/5/91 |s2cid=118492541}}</ref> {{val|772.33|2.42|u=mas}}, in the original [[Hipparcos]] Catalogue, in 1997;<ref name="aaa323_L49">{{cite journal |last1=Perryman |first1=M. A. C. |last2=Lindegren |first2=L. |last3=Kovalevsky |first3=J. |last4=Hoeg |first4=E. |last5=Bastian |first5=U. |last6=Bernacca |first6=P. L. |last7=Crézé |first7=M. |last8=Donati |first8=F. |last9=Grenon |first9=M. |last10=Grewing |first10=M. |last11=van Leeuwen |first11=F. |date=July 1997 |title=The Hipparcos catalogue |journal=Astronomy and Astrophysics |volume=323 |pages=L49–L52 |bibcode=1997A&A...323L..49P |last12=van der Marel |first12=H. |last13=Mignard |first13=F. |last14=Murray |first14=C. A. |last15=Le Poole |first15=R. S. |last16=Schrijver |first16=H. |last17=Turon |first17=C. |last18=Arenou |first18=F. |last19=Froeschlé |first19=M. |last20=Petersen |first20=C. S.}}</ref> {{val|771.64|2.60|u=mas}} in the Hipparcos New Reduction, in 2007;<ref name="hipparcos">{{cite journal |bibcode=2007A&A...474..653V |title=Validation of the new Hipparcos reduction |journal=Astronomy and Astrophysics |volume=474 |issue=2 |pages=653–664 |last1=Van Leeuwen |first1=F. |year=2007 |doi=10.1051/0004-6361:20078357 |arxiv=0708.1752|s2cid=18759600 }}</ref> and {{val|768.77|0.37|u=mas}} using the [[Hubble Space Telescope]]{{'s}} [[fine guidance sensor]]s, in 1999.<ref name="apj118" /> From Earth's vantage point, Proxima Centauri is separated from Alpha Centauri by 2.18 degrees,<ref name="apj121">{{cite journal |last1=Kirkpatrick |first1=J. D. |last2=Davy |first2=J. |last3=Monet |first3=David G. |last4=Reid |first4=I. Neill |last5=Gizis |first5=John E. |last6=Liebert |first6=James |last7=Burgasser |first7=Adam J. |year=2001 |title=Brown dwarf companions to G-type stars. I: Gliese 417B and Gliese 584C |journal=The Astronomical Journal |volume=121 |issue=6 |pages=3235–3253 |arxiv=astro-ph/0103218 |bibcode=2001AJ....121.3235K |doi=10.1086/321085 |s2cid=18515414}}</ref> or four times the angular diameter of the full [[Moon]].<ref>{{cite web |last=Williams |first=D. R. |date=February 10, 2006 |title=Moon Fact Sheet |url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html |access-date=October 12, 2007 |series=Lunar & Planetary Science |publisher=NASA}}</ref> Proxima Centauri has a relatively large proper motion—moving 3.85&nbsp;[[arcseconds]] per year across the sky.<ref>{{cite conference |last1=Benedict |first1=G. F. |last2=Mcarthur |first2=B. |last3=Nelan |first3=E. |last4=Story |first4=D. |last5=Jefferys |first5=W. H. |last6=Wang |first6=Q. |last7=Shelus |first7=P. J. |last8=Hemenway |first8=P. D. |last9=Mccartney |first9=J. |title=Astrometric stability and precision of fine guidance sensor #3: the parallax and proper motion of Proxima Centauri |url=http://clyde.as.utexas.edu/SpAstNEW/Papers_in_pdf/%7BBen93%7DEarlyProx.pdf |pages=380–384 |access-date=July 11, 2007 |first10=Wm. F. |last10=Van Altena |first11=R. |last11=Duncombe |first12=O. G. |last12=Franz |first13=L. W. |last13=Fredrick |work=Proceedings of the HST calibration workshop}}</ref> It has a [[radial velocity]] towards the Sun of 22.2&nbsp;km/s.<ref name="KervellaThévenin2017" /> From Proxima Centauri, the Sun would appear as a bright 0.4-magnitude star in the constellation [[Cassiopeia (constellation)|Cassiopeia]], similar to that of [[Achernar]] or [[Procyon]] from [[Earth]].<ref group="nb">The coordinates of the Sun would be diametrically opposite Proxima Centauri, at α={{RA|02|29|42.9487}}, δ={{DEC|+62|40|46.141}}. The absolute magnitude ''M<sub>v</sub>'' of the Sun is 4.83, so at a parallax ''π'' of 0.77199 the apparent magnitude ''m'' is given by 4.83 − 5(log<sub>10</sub>(0.77199) + 1) = 0.40.
See: {{cite book |last=Tayler |first=Roger John |url=https://archive.org/details/starstheirstruct00tayl_311 |title=The Stars: Their Structure and Evolution |date=1994 |publisher=Cambridge University Press |isbn=978-0-521-45885-6 |page=[https://archive.org/details/starstheirstruct00tayl_311/page/n24 16] |url-access=limited}}</ref>

Among the known stars, Proxima Centauri has been the closest star to the Sun for about 32,000&nbsp;years and will be so for about another 25,000&nbsp;years, after which Alpha Centauri A and Alpha Centauri B will alternate approximately every 79.91 years as the closest star to the Sun. In 2001, J. García-Sánchez ''et al.'' predicted that Proxima Centauri will make its closest approach to the Sun in approximately 26,700&nbsp;years, coming within {{convert|3.11|ly|pc|abbr=on}}.<ref name="aaa379">{{cite journal |last1=García-Sánchez |first1=J. |last2=Weissman |first2=P. R. |last3=Preston |first3=R. A. |last4=Jones |first4=D. L. |last5=Lestrade |first5=J.-F. |last6=Latham |first6=. W. |last7=Stefanik |first7=R. P. |last8=Paredes |first8=J. M. |date=2001 |title=Stellar encounters with the solar system |url=http://www.aanda.org/articles/aa/pdf/2001/44/aah2819.pdf |journal=Astronomy and Astrophysics |volume=379 |issue=2 |pages=634–659 |bibcode=2001A&A...379..634G |doi=10.1051/0004-6361:20011330 |doi-access=free}}</ref> A 2010 study by V. V. Bobylev predicted a closest approach distance of {{convert|2.90|ly|pc|abbr=on}} in about 27,400&nbsp;years,<ref name="al36_3_220">{{cite journal |last=Bobylev |first=V. V. |date=March 2010 |title=Searching for stars closely encountering with the solar system |journal=Astronomy Letters |volume=36 |issue=3 |pages=220–226 |arxiv=1003.2160 |bibcode=2010AstL...36..220B |doi=10.1134/S1063773710030060 |s2cid=118374161}}</ref> followed by a 2014 study by C. A. L. Bailer-Jones predicting a perihelion approach of {{convert|3.07|ly|pc|abbr=on}} in roughly 26,710&nbsp;years.<ref>{{cite journal |last=Bailer-Jones |first=C. A. L. |date=March 2015 |title=Close encounters of the stellar kind |journal=Astronomy & Astrophysics |volume=575 |pages=13 |arxiv=1412.3648 |bibcode=2015A&A...575A..35B |doi=10.1051/0004-6361/201425221 |id=A35 |s2cid=59039482}}</ref> Proxima Centauri is orbiting through the [[Milky Way]] at a distance from the [[Galactic Center|Galactic Centre]] that varies from {{convert|8.3|to|9.5|kpc|kly|order=flip|lk=on|abbr=on}}, with an [[orbital eccentricity]] of 0.07.<ref>{{cite journal |last1=Allen |first1=C.|author1-link=Christine Allen (astronomer) |last2=Herrera |first2=M. A. |date=1998 |title=The galactic orbits of nearby UV Ceti stars |journal=Revista Mexicana de Astronomía y Astrofísica |volume=34 |pages=37–46 |bibcode=1998RMxAA..34...37A}}</ref>

=== Alpha Centauri ===
{{Main|Alpha Centauri}}
Proxima Centauri has been suspected to be a companion of the Alpha Centauri [[binary star]] system since its discovery in 1915. For this reason, it is sometimes referred to as Alpha Centauri&nbsp;C. Data from the [[Hipparcos]] satellite, combined with ground-based observations, were consistent with the hypothesis that the three stars are a [[gravitationally bound]] system. Kervella et al. (2017) used high-precision radial velocity measurements to determine with a high degree of confidence that Proxima and Alpha Centauri are gravitationally bound.<ref name="KervellaThévenin2017" /> Proxima Centauri's orbital period around the Alpha Centauri&nbsp;AB [[barycenter]] is {{val|547000|6600|4000|fmt=commas}} years with an eccentricity of {{val|0.5|0.08}}; it approaches Alpha Centauri to {{val|4300|1100|900|u=AU|fmt=commas}} at [[periastron]] and retreats to {{val|13000|300|100|u=AU|fmt=commas}} at [[apastron]].<ref name="KervellaThévenin2017" /> At present, Proxima Centauri is {{convert|12947|±|260|AU|e12km|2|abbr=unit}} from the Alpha Centauri&nbsp;AB barycenter, nearly to the furthest point in its orbit.<ref name="KervellaThévenin2017" />

Six single stars, two binary star systems, and a triple star share a common motion through space with Proxima Centauri and the Alpha Centauri system. (The co-moving stars include [[HD 4391]], [[Gamma2 Normae|γ<sup>2</sup> Normae]], and [[Gliese 676]].) The [[space velocity (astronomy)|space velocities]] of these stars are all within 10&nbsp;km/s of Alpha Centauri's [[peculiar motion]]. Thus, they may form a [[moving group]] of stars, which would indicate a common point of origin, such as in a [[star cluster]].<ref>{{cite journal |last1=Anosova |first1=J. |last2=Orlov |first2=V. V. |last3=Pavlova |first3=N. A. |year=1994 |title=Dynamics of nearby multiple stars. The α Centauri system |journal=Astronomy and Astrophysics |volume=292 |issue=1 |pages=115–118 |bibcode=1994A&A...292..115A}}</ref>
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