This value comes from the rough average radii of the three largest stars studied in the paper. Theoretical limit of star size (Milky Way) List of the largest known stars in the Milky Way This list is incomplete you can help by adding missing items. Such stars may exceed accepted limits by undergoing large eruptions or changing their spectral types over just a few months (or potentially years). For example, some red supergiants in the Magellanic Clouds are suspected to have slightly different limiting temperatures and luminosities. In these lists are some examples of extremely distant extragalactic stars, which may have slightly different properties and natures than the currently largest known stars in the Milky Way.Most distance estimates for red supergiants come from stellar cluster or association membership, because it is difficult to calculate accurate distances for red supergiants that are not part of any cluster or association. This is only possible for a very small number of stars. Other direct methods for determining stellar radii rely on lunar occultations or from eclipses in binary systems.This makes adopted luminosities poorly known and may significantly change the quoted radii. Many extended supergiant atmospheres also significantly change in size over time, regularly or irregularly pulsating over several months or years as variable stars.Many supergiant stars have extended atmospheres, and many are within opaque dust shells, making their true effective temperatures and surfaces highly uncertain.Stellar distances, and their errors, for most stars, remain uncertain or poorly determined.Stellar radii or diameters are usually derived only approximately using the Stefan–Boltzmann law for the deduced stellar luminosity and effective surface temperature.The following lists are generally based on various considerations or assumptions these include: Various issues exist in determining accurate radii of the largest stars, which in many cases do display significant errors. The lists are still a work in progress and parameters are prone to change. Values for stellar radii vary significantly in different sources and for different observation methods.Īll the sizes stated in these lists have inaccuracies and may be disputed. Often stellar radii can only be expressed as an average or be within a large range of values. Uncertainties remain with the membership and order of the lists, especially when deriving various parameters used in calculations, such as stellar luminosity and effective temperature. Angular diameter measurements can be inconsistent because the boundary of the very tenuous atmosphere ( opacity) differs depending on the wavelength of light in which the star is observed. Examples of eclipsing binaries are Epsilon Aurigae (Almaaz), VV Cephei, and V766 Centauri (HR 5171). Only a few useful supergiant stars can be occulted by the Moon, including Antares A (Alpha Scorpii A). Other methods can use lunar occultations or from eclipsing binaries, which can be used to test indirect methods of finding stellar radii. The angular diameters of stars can be measured directly using stellar interferometry. ĭepending on models, several studies had predicted that high-accreting Population III or I supermassive stars (SMSs) in the very early universe could have evolved "red supergiant protostars" as high accretion rates would prevent stars to contract, resulting lower temperatures and radii reaching up to many tens of thousands of R ☉, comparable to some of the largest known black holes. Luminous red novae during mergebursts appears to expand extremely rapidly, reaching thousands to tens of thousands of solar radii within only a few months, significantly larger than the largest red supergiants. Some examples include Eta Carinae A during its so-called "Great Eruption". Overview Four well-defined large red supergiants and their respective sizes, including S Persei, AH Scorpii, VY Canis Majoris, and WOH G64.Īlthough red supergiants are often considered the largest normal stars, some other stars were found to have temporary increase significantly in radius during a transcient event for a short time (in cosmic scale), such as LBV eruptions or red novae. The unit of measurement used is the radius of the Sun (approximately 695,700 km 432,300 mi). ( Pistol Star, Rho Cassiopeiae, Betelgeuse, and VY Canis Majoris)īelow are lists of the largest stars currently known, ordered by radius and separated into categories by galaxy. The Sun, the orbit of Earth, Jupiter, and Neptune, compared to four stars. Not to be confused with List of most massive stars.
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