Editing Proxima Centauri (section)

== Structure and fusion ==
Because of its low mass, the interior of the star is completely [[Convection zone|convective]],<ref name=Yadav2016/> causing energy to be transferred to the exterior by the physical movement of plasma rather than through [[Radiation zone|radiative processes]]. This convection means that the helium ash left over from the [[thermonuclear fusion]] of hydrogen does not accumulate at the core but is instead circulated throughout the star. Unlike the Sun, which will only burn through about 10% of its total hydrogen supply before leaving the main sequence, Proxima Centauri will consume nearly all of its fuel before the fusion of hydrogen comes to an end.<ref name="adams">{{cite conference |last1=Adams |first1=Fred C. |last2=Laughlin |first2=Gregory |last3=Graves |first3=Genevieve J. M. |title=Red dwarfs and the end of the main sequence |url=http://www.astroscu.unam.mx/rmaa/RMxAC..22/PDF/RMxAC..22_adams.pdf |publisher=[[Revista Mexicana de Astronomía y Astrofísica]] |pages=46–49 |access-date=June 24, 2008 |work=Gravitational collapse: from massive stars to planets |archive-date=11 July 2019 |archive-url=https://web.archive.org/web/20190711072446/http://www.astroscu.unam.mx/rmaa/RMxAC..22/PDF/RMxAC..22_adams.pdf |url-status=dead }}</ref>

Convection is associated with the generation and persistence of a [[Stellar magnetic field|magnetic field]]. The magnetic energy from this field is released at the surface through [[stellar flare]]s that briefly (as short as per ten seconds)<ref name=MacGregor_et_al_2021>{{cite journal |arxiv=2104.09519 |last1=MacGregor |first1=Meredith A. |last2=Weinberger |first2=Alycia J. |last3=Parke Loyd |first3=R. O. |last4=Shkolnik |first4=Evgenya |last5=Barclay |first5=Thomas |last6=Howard |first6=Ward S. |last7=Zic |first7=Andrew |last8=Osten |first8=Rachel A. |last9=Cranmer |first9=Steven R. |last10=Kowalski |first10=Adam F. |last11=Lenc |first11=Emil |last12=Youngblood |first12=Allison |last13=Estes |first13=Anna |last14=Wilner |first14=David J. |last15=Forbrich |first15=Jan |last16=Hughes |first16=Anna |last17=Law |first17=Nicholas M. |last18=Murphy |first18=Tara |last19=Boley |first19=Aaron |last20=Matthews |first20=Jaymie |title=Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through Far-ultraviolet Observations |journal=The Astrophysical Journal Letters |year=2021 |volume=911 |issue=2 |pages=L25 |doi=10.3847/2041-8213/abf14c |bibcode=2021ApJ...911L..25M |s2cid=233307258 |doi-access=free }}</ref> increase the overall luminosity of the star. On May 6, 2019, a flare event bordering Solar [[Solar_flare#Soft X-ray classification|M and X flare class]],<ref>{{citation|arxiv=2209.05490|year=2022|title=The Mouse That Squeaked: A Small Flare from Proxima Cen Observed in the Millimeter, Optical, and Soft X-Ray with Chandra and ALMA|doi=10.3847/1538-4357/ac9134 |last1=Howard |first1=Ward S. |last2=MacGregor |first2=Meredith A. |last3=Osten |first3=Rachel |last4=Forbrich |first4=Jan |last5=Cranmer |first5=Steven R. |last6=Tristan |first6=Isaiah |last7=Weinberger |first7=Alycia J. |last8=Youngblood |first8=Allison |last9=Barclay |first9=Thomas |last10=Parke Loyd |first10=R. O. |last11=Shkolnik |first11=Evgenya L. |last12=Zic |first12=Andrew |last13=Wilner |first13=David J. |journal=The Astrophysical Journal |volume=938 |issue=2 |page=103 |bibcode=2022ApJ...938..103H |s2cid=252211788 |doi-access=free }}</ref> briefly became the brightest ever detected, with a far ultraviolet emission of {{val|2|e=30|u=erg}}.<ref name=MacGregor_et_al_2021/> These flares can grow as large as the star and reach temperatures measured as high as 27&nbsp;million [[Kelvin|K]]<ref name=aaa416>{{cite journal |last1=Guedel |first1=M. | last2=Audard | first2=M. | last3=Reale | first3=F. | last4=Skinner | first4=S. L. | last5=Linsky | first5=J. L. |title=Flares from small to large: X-ray spectroscopy of Proxima Centauri with XMM-Newton |journal=Astronomy and Astrophysics |date=2004 |volume=416 |issue=2 |pages=713–732 |arxiv=astro-ph/0312297 |doi=10.1051/0004-6361:20031471 |bibcode=2004A&A...416..713G|s2cid=7725125 }}</ref>—hot enough to radiate [[X-ray]]s.<ref>{{cite web |url=http://chandra.harvard.edu/photo/2004/proxima/ |title=Proxima Centauri: the nearest star to the Sun |publisher=Harvard-Smithsonian Center for Astrophysics |date=August 30, 2006 |access-date=July 9, 2007}}</ref> Proxima Centauri's quiescent X-ray luminosity, approximately (4–16){{E-sp|26}}&nbsp;[[erg]]/s ((4–16){{E-sp|19}}&nbsp;[[watt|W]]), is roughly equal to that of the much larger Sun. The peak X-ray luminosity of the largest flares can reach {{10^|28}}&nbsp;erg/s ({{10^|21}}&nbsp;W).<ref name=aaa416/>

Proxima Centauri's [[chromosphere]] is active, and its [[stellar spectrum|spectrum]] displays a strong [[Spectral line|emission line]] of singly ionized [[magnesium]] at a wavelength of 280&nbsp;[[Nanometre|nm]].<ref>{{cite journal |first1=Guinan |last1=E. F. |last2=Morgan |first2=N. D. |title=Proxima Centauri: rotation, chromospheric activity, and flares |journal=Bulletin of the American Astronomical Society |date=1996 |volume=28 |pages=942 |bibcode=1996AAS...188.7105G}}</ref> About 88% of the surface of Proxima Centauri may be active, a percentage that is much higher than that of the Sun even at the peak of the [[solar cycle]]. Even during quiescent periods with few or no flares, this activity increases the [[stellar corona|corona]] temperature of Proxima Centauri to 3.5&nbsp;million K, compared to the 2&nbsp;million K of the Sun's corona,<ref>{{cite journal | last1=Wargelin | first1=Bradford J. | last2=Drake | first2=Jeremy J. |title=Stringent X-ray constraints on mass loss from Proxima Centauri |journal=The Astrophysical Journal |date=2002 |volume=578 |issue=1 |pages=503–514 |doi=10.1086/342270 |bibcode=2002ApJ...578..503W|doi-access=free }}</ref> and its total X-ray emission is comparable to the sun's.<ref name=apj547/> Proxima Centauri's overall activity level is considered low compared to other red dwarfs,<ref name=apj547>{{cite journal | last1=Wood | first1=B. E. | last2=Linsky | first2=J. L. | last3=Müller | first3=H.-R. | last4=Zank | first4=G. P. |title=Observational estimates for the mass-loss rates of α Centauri and Proxima Centauri using Hubble Space Telescope Lyα spectra |journal=The Astrophysical Journal |date=2001 |volume=547 |issue=1 |pages=L49–L52 |doi=10.1086/318888 |bibcode=2001ApJ...547L..49W |arxiv=astro-ph/0011153|s2cid=118537213 }}</ref> which is consistent with the star's estimated age of 4.85{{E-sp|9}}&nbsp;years,<ref name="ESO2003"/> since the activity level of a red dwarf is expected to steadily wane over billions of years as its [[stellar rotation]] rate decreases.<ref>{{cite journal |last1=Stauffer |first1=J. R. | last2=Hartmann | first2=L. W. |title=Chromospheric activity, kinematics, and metallicities of nearby M dwarfs |journal=Astrophysical Journal Supplement Series |date=1986 |volume=61 |issue=2 |pages=531–568 |bibcode=1986ApJS...61..531S |doi=10.1086/191123|doi-access=free }}</ref> The activity level appears to vary<ref>{{Cite news |last=Pulliam |first=Christine |url=http://insider.si.edu/2016/10/proxima-centauri-might-sunlike-thought/ |title=Proxima Centauri Might Be More Sunlike Than We Thought |date=October 12, 2016 |work=Smithsonian Insider |access-date=July 7, 2020}}</ref> with a period of roughly 442 days, which is shorter than the Sun's solar cycle of 11 years.<ref>{{cite journal | last1=Cincunegui | first1=C. | last2=Díaz | first2=R. F. | last3=Mauas | first3=P. J. D. |title=A possible activity cycle in Proxima Centauri |journal=Astronomy and Astrophysics |date=2007 |volume=461 |issue=3 |pages=1107–1113 |doi=10.1051/0004-6361:20066027 |bibcode=2007A&A...461.1107C |arxiv=astro-ph/0703514|s2cid=14672316 }}</ref>

Proxima Centauri has a relatively weak [[stellar wind]], no more than 20% of the mass loss rate of the [[solar wind]]. Because the star is much smaller than the Sun, the mass loss per unit surface area from Proxima Centauri may be eight times that from the Sun's surface.<ref>{{cite journal |last1=Wood |first1=B. E. | last2=Linsky | first2=J. L. | last3=Muller | first3=H.-R. | last4=Zank | first4=G. P. |title=Observational estimates for the mass-loss rates of Alpha Centauri and Proxima Centauri using Hubble Space Telescope Lyman-alpha spectra |journal=Astrophysical Journal |date=2000 |volume=537 |issue=2 |pages=L49–L52 |arxiv=astro-ph/0011153 |doi=10.1086/309026 |bibcode=2000ApJ...537..304W|s2cid=119332314 }}</ref>