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2MASS image of red supergiant star UY Scuti (brightest star in the image), surrounded by a dense starfield. This picture was published in 2003.

An illustration of the approximate size of UY Scuti compared to the Sun.

Relative sizes of the planets in the Solar System and several stars, including UY Scuti

UY Scuti is a red hypergiant nearly 9,500 light years away from Earth in the constellation of Scutum. The star is really big, nearly 1,708 times the diameter of the Sun and also one of the most luminous stars, 350.000 brighter than the Sun. It located in the same constellation with Stephenson 2-18, but UY Scuti is named after the constellation as it was studied and known as the largest star before Stephenson 2-18. UY Scuti is recently thought by some to be 755 - 775 the diameter of the Sun and 5,400 light years away from Earth, rather than 1,708 times the diameter of the Sun and 9,500 light years away, but these new stats were proven wrong and we know that UY Scuti's diameter is 1,708 the Sun's and it's distance is 9,500 light years.


UY Scuti is larger than many stars in the universe, one of the largest ever found. It is 1,708 the diameter of the Sun. Inside UY Scuti, at least 5 billion Suns are thought to fit. However, UY Scuti is larger than VY Cnais Majoris, which is thought to fit 6.8 billion Suns, thus UY Scuti can likely fit more than 7 billion Suns or more inside it. UY Scuti was the largest star known as of recently, as of August 2020, when it's crown was stolen by Stephenson 2-18.


UY Scuti's mass is estimated to be around 30 times the mass of the Sun, making UY Scuti much more massive than Stephenson 2-18, which is thought to have a mass of about 12 to 16 times the mass of the Sun. Likely Stephenson 2-18 lost mass before UY Scuti, as this star is probably older than Uy Scuti, meaning that UY Scuti is likely gonna lose more mass while expanding in size. Like Stephenson 2-18, UY Scuti currently fuses helium to carbon. It burns quickly through it's mass.


UY Scuti is nearly 350.000 times the luminosity of the Sun. It is unknown why UY Scuti is not as bright as Stephenson 2-18, since Stephenson 2-18 is lager than UY Scuti, 2,150 times the diameter of the Sun, compared to 1,708 the diameter of the Sun for UY Scuti, but yet UY Scuti is much more massive than Stephenson 2-18, being around 30 times the Sun's mass, compared to 12 to 16 times the Sun's mass for Stephenson 2-18.

UY Scuti's surface temperature is nearly 3,365 Kelvin, about 3091 °C.

See also

  1. Wikipedia article:
  2. Kids learning tube:
  3. Old video of Anton Petrov:
  4. Stephenson 2-18: Stephenson 2-18