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Below are lists of the largest stars currently known, ordered by radius and separated into categories by galaxy. The unit of measurement used is the radius of the Sun (approximately 695,700 km; 432,300 mi). [1] The Sun, the orbit of Earth, Jupiter, and Neptune, compared to four stars (Pistol Star, Rho Cassiopeiae, Betelgeuse, and VY Canis Majoris)
The astronomical system of units, formerly called the IAU (1976) System of Astronomical Constants, is a system of measurement developed for use in astronomy.It was adopted by the International Astronomical Union (IAU) in 1976 via Resolution No. 1, [1] and has been significantly updated in 1994 and 2009 (see Astronomical constant).
In addition to being far away, many stars of such extreme mass are surrounded by clouds of outflowing gas created by extremely powerful stellar winds; the surrounding gas interferes with the already difficult-to-obtain measurements of stellar temperatures and brightnesses, which greatly complicates the issue of estimating internal chemical ...
Stars range in size from neutron stars, which vary anywhere from 20 to 40 km (25 mi) in diameter, to supergiants like Betelgeuse in the Orion constellation, which has a diameter about 640 times that of the Sun [140] with a much lower density. [141]
Early photometric measurements (made, for example, by using a light to project an artificial “star” into a telescope's field of view and adjusting it to match real stars in brightness) demonstrated that first magnitude stars are about 100 times brighter than sixth magnitude stars.
Main-sequence stars vary in surface temperature from approximately 2,000 to 50,000 K, whereas more-evolved stars – in particular, newly-formed white dwarfs – can have surface temperatures above 100,000 K. [3] Physically, the classes indicate the temperature of the star's atmosphere and are normally listed from hottest to coldest.
Betelgeuse became the first extrasolar star whose photosphere's angular size was measured in 1920, and subsequent studies have reported an angular diameter (i.e., apparent size) ranging from 0.042 to 0.056 arcseconds; that range of determinations is ascribed to non-sphericity, limb darkening, pulsations and varying appearance at different ...
Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. ... Measurements Evolution of the ... (largest known star ...