Editing Antares (section)

===Antares===
[[File:VLTI reconstructed view of the surface of Antares.jpg|thumb|left|[[VLTI]] reconstructed view of the surface of Antares A|alt=]]
Antares is a red [[supergiant star]] with a [[stellar classification]] of M1.5Iab-Ib, and is indicated to be a spectral standard for that class.<ref name="perkins" /> Due to the nature of the star, the derived [[parallax]] measurements have large errors, so that the true distance of Antares is approximately {{convert|550|ly|pc|abbr=off|lk=on}} from the Sun.<ref name="aaa474_2_653" />

The [[Absolute magnitude|brightness]] of Antares at visual wavelengths is about 10,000 times that of the [[Sun]], but because the star radiates a considerable part of its energy in the [[infrared]] part of the [[electromagnetic spectrum|spectrum]], the true [[bolometric luminosity]] is around 100,000 times that of the Sun. There is a large margin of error assigned to values for the bolometric luminosity, typically 30% or more. There is also considerable variation between values published by different authors, for example {{solar luminosity|75,900}} and {{solar luminosity|97,700}} published in 2012 and 2013.<ref name="Pecaut" /><ref name="ohnaka2013" />

The mass of the star has been calculated to be about {{solar mass|12}},<ref name="Pecaut" /> or {{solar mass|11 to 14.3}}.<ref name="ohnaka2013" /> Comparison of the [[effective temperature]] and luminosity of Antares to theoretical evolutionary tracks for massive stars suggest a progenitor mass of {{solar mass|17}} and an age of 12 million years (MYr),<ref name="Pecaut" /> or an initial mass of {{solar mass|15}} and an age of 11 to 15 MYr.<ref name="ohnaka2013" /> Comparison of observations from antiquity to theoretical evolutionary tracks suggests an initial mass of {{Solar mass|15 to 16}}, or the possibility that Antares is on a [[blue loop]] with an initial mass of {{Solar mass|13}} (while excluding {{Solar mass|14}} as a possible mass estimate). These correspond to ages from 11.8 to 17.3 MYr.<ref name="Neuhäuser_et_al_2022" /> These initial mass estimates mean that Antares may have once resembled massive blue stars like the members of the [[Acrux]] system, which have similar initial masses (both Antares and Acrux are members of the wider [[Scorpius–Centaurus association]]).<ref>{{Cite journal |last=Tokovinin |first=A. A. |date=1997-07-01 |title=MSC - a catalogue of physical multiple stars |url=https://aas.aanda.org/articles/aas/abs/1997/10/ds1218/ds1218.html |journal=Astronomy and Astrophysics Supplement Series |language=en |volume=124 |issue=1 |pages=75–84 |doi=10.1051/aas:1997181 |bibcode=1997A&AS..124...75T |issn=0365-0138}}</ref> Massive stars like Antares are expected to explode as [[supernova]]e.<ref name="Hockey2010" />

Like most cool supergiants, Antares's size has much uncertainty due to the tenuous and translucent nature of the extended outer regions of the star. Defining an effective temperature is difficult due to spectral lines being generated at different depths in the atmosphere, and linear measurements produce different results depending on the wavelength observed.<ref name="Ireland2004" /> In addition, Antares pulsates in size, varying its radius by 19%.<ref name="Pecaut" /> It also varies in temperature by 150 K, lagging 70 days behind [[radial velocity]] changes which are likely to be caused by the pulsations.<ref name="pugh2013" />

The diameter of Antares can be measured most accurately using [[interferometry]] or observing [[Occultation|lunar occultation]]s events. An apparent diameter from occultations 41.3 ± 0.1 [[Minute and second of arc#Symbols and abbreviations|milliarcseconds]] has been published.<ref name="richichi" /> Interferometry allows synthesis of a view of the stellar disc, which is then represented as a [[Limb darkening|limb-darkened]] disk surrounded by an extended atmosphere. The diameter of the limb-darkened disk was measured as {{val|37.38|0.06|u=milliarcseconds}} in 2009 and {{val|37.31|0.09|u=milliarcseconds}} in 2010. The linear radius of the star can be calculated from its angular diameter and distance. However, the distance to Antares is not known with the same accuracy as modern measurements of its diameter.

An estimate obtained by interferometry in 1925 by [[Francis G. Pease]] at the [[Mount Wilson Observatory]] gave Antares a diameter of {{convert|400 to 430|e6mi|e6km|abbr=unit}}, equal to approximately {{Solar radius|463-497}}, making it the then [[List of largest known stars|largest star known]].<ref>{{Cite journal |date=1925 |title=Science News |url=https://www.jstor.org/stable/1650052 |journal=Science |volume=61 |issue=1576 |pages=x–xiv |jstor=1650052 |issn=0036-8075}}</ref><ref>{{Cite journal |last=Pease |first=F. G. |date=1921 |title=The Diameter of Alpha Scorpii by the Interferometer Method |url=https://www.jstor.org/stable/40671460 |journal=Publications of the Astronomical Society of the Pacific |volume=33 |issue=194 |pages=204–205 |doi=10.1086/123081 |jstor=40671460 |bibcode=1921PASP...33..204P |issn=0004-6280}}</ref> Antares is now known to be somewhat larger;<ref>{{Cite conference |last=Wing |first=R. F. |date=2009-09-01 |title=The Biggest Stars of All | conference=The Biggest, Baddest, Coolest Stars. Proceedings of the workshop held 16-18 July 2007, at the Millennium Centre, Johnson City, Tennessee, USA | series= ASP Conference Series | editor1-first=Donald G. | editor1-last=Luttermoser | editor2-first=Beverly J. | editor2-last=Smith | editor3-first=Robert E. | editor3-last=Stencel | bibcode=2009ASPC..412..113W |volume=412 |pages=113}}</ref> for instance, the [[Hipparcos]] satellite's [[parallax|trigonometric parallax]] of {{val|5.89|1.00|u=mas}}<ref name="HIPPARCOS" /> with modern angular diameter estimates lead to a radius of about {{solar radius|680}}.<ref name="ohnaka2013" /> Older radii estimates exceeding {{solar radius|850}} were derived from older measurements of the diameter,<ref name="pugh2013" /> but those measurements are likely to have been affected by asymmetry of the atmosphere and the narrow range of infrared wavelengths observed; Antares has an extended shell which radiates strongly at those particular wavelengths.<ref name="ohnaka2013" /> Despite its large size compared to the Sun, Antares is dwarfed by even larger red supergiants, such as [[VY Canis Majoris]], [[KY Cygni]], [[RW Cephei]] or [[Mu Cephei]].

Antares, like the similarly sized red supergiant [[Betelgeuse]] in the constellation [[Orion (constellation)|Orion]], will almost certainly explode as a [[supernova]],<ref name="Firestone2014" /> probably in {{val|1.0|to|1.4}} million years.<ref name="Neuhäuser_et_al_2022"/> For a few months, the Antares supernova could be as bright as the full moon and be visible in daytime.<ref name="Hockey2010" />