Editing Betelgeuse (section)

== Binarity ==
Betelgeuse generally has been considered to be a single isolated star and a [[runaway star]], not currently associated with any cluster or star-forming region, although its birthplace is unclear.<ref name=vanloon>{{cite journal |bibcode=2013EAS....60..307V |title=Betelgeuse and the Red Supergiants |journal=Betelgeuse Workshop 2012 |editor-first=P. |editor-last=Kervella |volume=60 |pages=307–316 |last1=Van Loon |first1=J. Th. |year=2013 |doi=10.1051/eas/1360036 |arxiv=1303.0321 |citeseerx=10.1.1.759.580 |s2cid=118626509}}</ref> However, starting in 1985, three studies have proposed companion stars to Betelgeuse. In 1985, analysis of [[Polarization (waves)|polarization]] data from 1968 through 1983 indicated a close companion with a periodic orbit of about 2.1&nbsp;years, and by using [[Speckle imaging|speckle interferometry]], the team concluded that the closer of the two companions was located at {{val|0.06|0.01|u="}} (≈9&nbsp;AU) from the main star with a position angle of 273°, an orbit that would potentially place it within the star's [[chromosphere]]. The more distant companion was at {{val|0.51|0.01|u="}} (≈77&nbsp;AU) with a position angle of 278°.<ref name=KAROVSKA1>{{cite journal| title=On a possible close companion to {{nobr|{{mvar|α}} Ori}} | author1=Karovska, M. | author2=Noyes, R.W.| author3=Roddier, F. | author4=Nisenson, P.| author5=Stachnik, R.V.| journal=Bulletin of the American Astronomical Society| volume=17| page=598| year=1985| bibcode=1985BAAS...17..598K}}</ref><ref name=KAROVSKA2>{{cite journal| title=On the alpha Orionis triple system| author1=Karovska, M.| author2=Nisenson, P.| author3=Noyes, R.| journal=Astrophysical Journal| volume=308 | pages=675–85| year=1986| doi=10.1086/164497| bibcode=1986ApJ...308..260K}}</ref> Other studies have found no evidence for these companions or have actively refuted their existence,<ref name="WILSON2">{{cite journal| title=High-resolution imaging of Betelgeuse and Mira| author1=Wilson, R. W.| author2=Baldwin, J. E.| author3=Buscher, D. F.| author4=Warner, P. J.| journal=Monthly Notices of the Royal Astronomical Society| volume=257 | issue=3 | pages=369–76| year=1992| bibcode=1992MNRAS.257..369W| doi=10.1093/mnras/257.3.369 | doi-access=free}}</ref> but the possibility of a close companion contributing to the overall flux has never been fully ruled out.<ref name="HAUBOIS"/> High-resolution interferometry of Betelgeuse and its vicinity, far beyond the technology of the 1980s and 1990s, has not detected any companions.<ref name=KERVELLA2009/><ref name=montarges2016/>

More recently, in 2024, two studies found evidence for a companion star. One study found that a not yet directly-observed, dust-modulating star or [[compact object]] of {{val|1.17|0.07|ul=Solar mass}} at a distance of {{val|8.60|0.33}}&nbsp;[[Astronomical unit|AU]] would be the most likely solution for Betelgeuse's 2170-day secondary periodicity, fluctuating radial velocity, moderate radius and low variation in effective temperature.<ref name="Goldberg2024">
{{Cite journal |last1=Goldberg |first1=Jared A. |last2=Joyce |first2=Meridith |last3=Molnár |first3=László |date=November 2024 |title=A buddy for Betelgeuse: Binarity as the origin of the long secondary period in {{nobr|{{mvar|α}} Orionis}} |journal=The Astrophysical Journal |language=en |volume=977 |issue=1 |pages=35 |doi=10.3847/1538-4357/ad87f4 |doi-access=free |arxiv=2408.09089 |bibcode=2024ApJ...977...35G |issn=0004-637X}}</ref> A second study produced by a different group of researchers examined observational data spanning a century, also suggesting a close-in stellar companion, possibly less massive and luminous than the Sun with an orbital period of 5.78 years. It is expected to be engulfed by Betelgeuse within 10,000 years.<ref name=MacLeod2024>{{cite journal |last1=MacLeod |first1=Morgan |last2=Blunt |first2=Sarah |last3=De Rosa |first3=Robert J. |last4=Dupree |first4=Andrea K. |last5=Granzer |first5=Thomas |last6=Harper |first6=Graham M. |last7=Huang |first7=Caroline D. |last8=Leiner |first8=Emily M. |last9=Loeb |first9=Abraham |last10=Nielsen |first10=Eric L. |last11=Strassmeier |first11=Klaus G. |last12=Wang |first12=Jason J. |last13=Weber |first13=Michael |title=Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse |journal=The Astrophysical Journal |date=2024 |volume=978 |issue=1 |page=50 |doi=10.3847/1538-4357/ad93c8 |doi-access=free |bibcode=2025ApJ...978...50M |arxiv=2409.11332 }}</ref>