Editing Alpha Centauri (section)

==== Alpha Centauri AB System ====
[[File:Best image of Alpha Centauri A and B.jpg|thumb| {{nobr|α Centauri A}} (left) is of the same [[stellar classification|stellar type]]&nbsp;G2 as the Sun, while {{nobr|α Centauri B}} (right) is a K1-type star.<ref>{{cite web|title=Best image of Alpha Centauri A and B |url=http://www.spacetelescope.org/images/potw1635a/|website=spacetelescope.org|access-date=29 August 2016}}</ref>|alt=Two white disks side by side, each with coloured fringes and prominent diffraction spikes]]
===== Alpha Centauri A =====
'''Alpha Centauri A''', also known as '''Rigil Kentaurus''', is the principal member, or primary, of the binary system. It is a solar-like [[main sequence|main-sequence]] star with a similar yellowish colour,<ref name="csiro">{{cite web |title=The colour of stars |date=21 December 2004 |website=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html|access-date=16 January 2012|url-status=dead|archive-url=https://web.archive.org/web/20120222183238/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=22 February 2012}}</ref> whose [[stellar classification]] is [[spectral type]] G2-V;<ref name=torres2006/> it is about 10% more massive than the Sun,<ref name="Thevenin02"/> with a radius about 22% larger.<ref name=kervella2017>{{cite journal |title=The radii and limb darkenings of α Centauri A and B. Interferometric measurements with VLTI/PIONIER |journal=Astronomy & Astrophysics |first1=P. |last1=Kervella |first2=L. |last2=Bigot |first3=A. |last3=Gallenne |first4=F. |last4=Thévenin |volume=597 |page=A137 |date=January 2017 |doi=10.1051/0004-6361/201629505 |bibcode=2017A&A...597A.137K
|arxiv=1610.06185 |s2cid=55597767}}</ref> When considered among the individual [[List of brightest stars|brightest stars]] in the night sky, it is the fourth-brightest at an apparent magnitude of +0.01,<ref name="ducati"/> being slightly fainter than [[Arcturus]] at an [[apparent magnitude]] of −0.05.

The type of [[magnetic activity]] on Alpha Centauri A is comparable to that of the Sun, showing [[stellar corona|coronal]] variability due to [[star spot]]s, as modulated by the rotation of the star. However, since 2005 the activity level has fallen into a deep minimum that might be similar to the Sun's historical [[Maunder Minimum]]. Alternatively, it may have a very long stellar activity cycle and is slowly recovering from a minimum phase.<ref name="Ayres2014">{{cite journal|title=The Ups and Downs of α Centauri|last1=Ayres|first1=Thomas R.|journal=The Astronomical Journal|arxiv=1401.0847|volume=147|issue=3|id=59
|page=12|date=March 2014|doi=10.1088/0004-6256/147/3/59|bibcode=2014AJ....147...59A|s2cid=117715969}}</ref>

===== Alpha Centauri B =====
{{hatnote group|
{{about-distinguish|α Centauri B, also known as Toliman|Beta Centauri{{!}}β Centauri|HD 102964{{!}}B Centauri|HD 129116{{!}}b Centauri|section=yes}}{{other uses|Toliman (disambiguation)}}
}}
'''Alpha Centauri B''', also known as '''Toliman''', is the secondary star of the binary system. It is a main-sequence star of spectral type K1-V, making it more an orange colour than Alpha Centauri A;<ref name="csiro"/> it has around 90% of the mass of the Sun and a 14% smaller diameter. Although it has a lower luminosity than A, Alpha Centauri B emits more energy in the [[X-ray]] band.<ref name="Xrays"/> Its [[light curve]] varies on a short time scale, and there has been at least one observed [[Flare star|flare]].<ref name="Xrays">{{cite journal|last1=Robrade|first1=J.|last2=Schmitt|first2=J. H. M. M.|last3=Favata|first3=F.
|year=2005|title=X-rays from α Centauri – The darkening of the solar twin|journal=Astronomy and Astrophysics|volume=442|issue=1|pages=315–321|bibcode=2005A&A...442..315R|doi=10.1051/0004-6361:20053314 |arxiv=astro-ph/0508260|s2cid=119120}}</ref> It is more magnetically active than Alpha Centauri A, showing a cycle of {{Val|8.2|0.2|u=yr}} compared to 11 years for the Sun, and has about half the minimum-to-peak variation in coronal luminosity of the Sun.<ref name="Ayres2014"/> This cycle was recently re-estimated based on more than 20 years of high-resolution spectroscopic observations of the CaIIH&K lines showing a cycle of {{Val|7.8|0.2|u=yr}}.<ref name="Cretignier2024">{{cite journal|last1=Cretignier|first1=M.|last2=Hara|first2=N.|last3=Pietrow|first3=A.G.M.|year=2024|title=Stellar surface information from the Ca II H&K lines - II. Defining better activity proxies|journal=Monthly Notices of the Royal Astronomical Society|volume=535|issue=1|pages=2562–2584|bibcode=2024MNRAS.535.2562C|doi= 
10.1093/mnras/stae2508 |doi-access=free |arxiv=astro-ph/0508260|s2cid=119120}}</ref> Alpha Centauri B has an apparent magnitude of +1.35, slightly dimmer than [[Mimosa (star)|Mimosa]].<ref name="IAU-LSN"/>