Editing Barnard's Star (section)

==Stellar flares==
===1998===
In 1998 a [[stellar flare]] on Barnard's Star was detected based on changes in the [[spectral emissions]] on 17 July during an unrelated search for variations in the proper motion. Four years passed before the flare was fully analyzed, at which point it was suggested that the flare's temperature was 8,000{{nbsp}}K, more than twice the normal temperature of the star.<ref name=Paulson>{{cite journal|first1=Diane B.|last1=Paulson|year=2006|title=Optical Spectroscopy of a Flare on Barnard's Star|journal=[[Publications of the Astronomical Society of the Pacific]]|volume=118|issue=1|page=227|doi=10.1086/499497|last2=Allred|first2=Joel C.|last3=Anderson|first3=Ryan B.|last4=Hawley|first4=Suzanne L.|last5=Cochran|first5=William D.|last6=Yelda|first6=Sylvana|bibcode=2006PASP..118..227P|arxiv=astro-ph/0511281|s2cid=17926580}}</ref> Given the essentially random nature of flares, Diane Paulson, one of the authors of that study, noted that "the star would be fantastic for amateurs to observe".<ref name=Flare/>

The flare was surprising because intense stellar activity is not expected in stars of such age. Flares are not completely understood, but are believed to be caused by strong [[magnetic field]]s, which suppress [[plasma (physics)|plasma]] [[convection]] and lead to sudden outbursts: strong magnetic fields occur in rapidly rotating stars, while old stars tend to rotate slowly. For Barnard's Star to undergo an event of such magnitude is thus presumed to be a rarity.<ref name=Paulson/> Research on the star's periodicity, or changes in stellar activity over a given timescale, also suggest it ought to be quiescent; 1998 research showed weak evidence for periodic variation in the star's brightness, noting only one possible starspot over 130 days.<ref name=Benedict1998>{{cite journal|last1=Benedict|first1=G. Fritz|year=1998|title=Photometry of Proxima Centauri and Barnard's star using Hubble Space Telescope fine guidance senso 3|journal=The Astronomical Journal|bibcode=1998AJ....116..429B|volume=116|issue=1|page=429|doi=10.1086/300420|last2=McArthur|first2=Barbara|last3=Nelan|first3=E.|last4=Story|first4=D.|last5=Whipple|first5=A. L.|last6=Shelus|first6=P. J.|last7=Jefferys|first7=W. H.|last8=Hemenway|first8=P. D.|last9=Franz|first9=Otto G.|last10=Wasserman|first10=L. H.|last11=Duncombe|first11=R. L.|last12=Van Altena|first12=W.|last13=Fredrick|first13=L. W.|arxiv=astro-ph/9806276|s2cid=15880053}}</ref>

Stellar activity of this sort has created interest in using Barnard's Star as a proxy to understand similar stars. It is hoped that photometric studies of its [[X-ray]] and [[UV]] emissions will shed light on the large population of old M dwarfs in the galaxy. Such research has [[astrobiological]] implications: given that the habitable zones of M dwarfs are close to the star, any planet located therein would be strongly affected by solar flares, [[stellar wind]]s, and plasma ejection events.<ref name=Riedel2005/>

===2019===
In 2019, two additional ultraviolet [[stellar flare]]s were detected, each with far-ultraviolet energy of 3×10<sup>22</sup> joules, together with one X-ray [[stellar flare]] with energy 1.6×10<sup>22</sup> joules. The flare rate observed to date is enough to cause loss of 87 Earth atmospheres per billion years through thermal processes and ≈3 Earth atmospheres per billion years through ion loss processes on Barnard's Star b.<ref>{{cite journal|last1=France|first1=Kevin|last2=Duvvuri|first2=Girish|last3=Egan|first3=Hilary|last4=Koskinen|first4=Tommi|last5=Wilson|first5=David J.|last6=Youngblood|first6=Allison|last7=Froning|first7=Cynthia S.|last8=Brown|first8=Alexander|last9=Alvarado-Gomez|first9=Julian D.|last10=Berta-Thompson|first10=Zachory K.|last11=Drake|first11=Jeremy J.|last12=Garraffo|first12=Cecilia|last13=Kaltenegger|first13=Lisa|last14=Kowalski|first14=Adam F.|last15=Linsky|first15=Jeffrey L.|last16=Loyd|first16=R. O. Parke|last17=Mauas|first17=Pablo J. D.|last18=Miguel|first18=Yamila|last19=Pineda|first19=J. Sebastian|last20=Rugheimer|first20=Sarah|last21=Schneider|first21=P. Christian|last22=Tian|first22=Feng|last23=Vieytes|first23=Mariela|arxiv=2009.01259|title=The High-Energy Radiation Environment Around a 10 Gyr M Dwarf: Habitable at Last?|journal=The Astronomical Journal|date=2 Sep 2020|volume=160|issue=5|page=237|doi=10.3847/1538-3881/abb465|bibcode=2020AJ....160..237F|s2cid=225282584 |doi-access=free }}</ref>