large star in space

Meet The 5 Biggest Stars in The Universe

Last Updated: December 17, 2021

While the Sun is the largest object in our solar system, it’s not a particularly large star. With a radius of 432,000 miles (690,000 km), and a temperature range from ~1.7 million °F (~1 million °C) to more than ~17 million °F (~10 million °C) in its outermost layer, the Sun belongs to a category of stars called the “yellow dwarfs” or “G-type main sequence stars”. O, B. A and F type main sequence stars, Giants and Supergiants all have larger radii than the Sun. If the Sun is a small star, what are the biggest stars in the universe? 

When we talk about a star’s size, we can either discuss its diameter (radius) or its mass. In both cases, the size of a star is compared to the size of our Sun. There are several methods for calculating stellar angular diameter and different methods may result in different stellar diameters for the same star. Additionally, a star’s size may vary over time. Most stellar radii are expressed as either averages or ranges and lists of largest stars have changed as techniques are refined. 

The best way to view these largest stars is with a telescope. This list includes the constellations to give you an idea of where in the sky to look. Let’s see what the largest stars are and where to find them.

1. UY Scuti

  • Constellation: Scutum
  • Radius: 1,708±192 solar radii
  • Diameter: 1.4766 billion miles / 2.3765 billion km
  • Distance: 9500 light-years
  • Celestial Coordinates: RA 18h 28m 49s | Dec -12° 27’ 10”

How To Find This Star: UY Scuti is located on the outside of Scutum, ~4.5°southwest from,  Alpha Scuti (apparent magnitude 3.85), and ~2° northwest from Gamma Scuti (apparent magnitude 4.69).

UY Scuti is a red hypergiant with an apparent magnitude of 9.31. A hypergiant is a rare type of star with an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. UY Scuti is also a pulsating semi-regular variable star whose magnitude varies from 11.2 to 13.3 over a period of 740.0 days. Its mass is 23.0 solar masses and it’s 47% cooler than the Sun. This star was first cataloged in 1860.

UY Scuti size comparison with the Sun

Image credits: Martin Silvertant

2. V766 Centauri Aa

  • Constellation: Centaurus
  • Radius: 1,492±540 solar radii
  • Diameter: 959.8 million miles / 1.5446 billion km
  • Distance: 4,900 – 11,700 light-years
  • Celestial Coordinates: RA 13h 48m 43s | Dec -62° 41’ 51”

How To Find This Star: V766 Centauri is located outside of Centaurus, ~2.5°southwest from Beta Centauri (apparent magnitude 0.63). 

V766 Centauri’s primary star (Aa) is a yellow hypergiant with an apparent magnitude of 6.90. It’s a semi-regular variable whose magnitude varies from 6.17 to 7.50 over a period of 494.0 days. Its mass is 13.0 solar masses and its temperature is 21% cooler than the Sun. A secondary component is located 9.3 arcseconds away and has an apparent magnitude of 9.89.

3. KY Cygni

  • Constellation: Cygnus
  • Radius: 1,420±284(–2,850±570) solar radii
  • Diameter: 1.227 billion miles / 1.976 billion km
  • Distance: 5000 light-years
  • Celestial Coordinates: RA 20h 26m 46s | Dec 38° 25’ 23”

How To Find This Star: KY Cygni is located below the crossbeam of the Northern Cross asterism, ~2° from Gamma Cygni (apparent magnitude 2.23) and ~6° from Epsilon Cygni (apparent magnitude 2.49).

KY Cygni is a red supergiant with an apparent magnitude of 10.87. It’s also a pulsating long-period variable star whose magnitude varies from 13.5 to 15.5. KY Cygni was discovered in 1930.

KY Cygni size comparison

Image Credit: Roy Britt / Space.com

4. AH Scorpii

  • Constellation: Scorpius
  • Radius: 1,411±124 solar radii
  • Diameter: 1.219 billion miles / 1.963 billion km
  • Distance: 1060 light-years
  • Celestial Coordinates: RA 17h 12m 41s | Dec -32° 21’ 5”

How To Find This Star: AH Scorpii is located above the Fishhook asterism, ~6.5° from Lambda Scorpii (apparent magnitude 1.62) and ~5° from Epsilon Scorpii (apparent magnitude 2.28). 

AH Scorpii is a red giant with an apparent magnitude of 8.19. This pulsating semi-regular variable star ranges in magnitude from 8.1 to 12.0 over a period of 713.6 days. Its mass is 1.2 solar masses and it’s 40% cooler than the Sun.

5. VV Cephei

  • Constellation: Cepheus
  • Radius: 1,329.62 solar radii
  • Diameter: 1.150 billion miles / 1.851 billion km
  • Distance: 163081.67 light-years
  • Celestial Coordinates: RA 22h 37m 17s | Dec +58° 32’ 18”

How To Find This Star: W Cephei is located near the bottom of Cepheus. Draw an imaginary line from Zeta Cephei (apparent magnitude 3.33) to Delta Cephei (apparent magnitude 4.07) then extend this line ~1° to W Cephei. 

W Cephei is an orange-red supergiant with an apparent magnitude of 7.57. It’s also a variable double star. The primary is a pulsating semi-regular star ranging in magnitude from 7.02 to 9.20. The secondary component is 0.4 arcminutes away and has a magnitude of 8.89. The primary has a mass of 13.0 solar masses and is 21% cooler than the Sun. While W Cephei was cataloged in 1896, it wasn’t known to be an eclipsing binary until 1936.

List of the 25 largest stars in the universe

The table below provides some interesting information about the 25 largest stars in the universe. You can download a copy of this table as a CSV file by clicking on the following link. (“File” -> “Download”)

RankNameSize (solar radii)Distance (ly)RADec
1UY Scuti1,708±192950018h 28m -12.5°
2V766 Centauri Aa1,492±5404,900 – 11,70013h 47m-62.6°
3KY Cygni1,420±284(–2,850±570)500020h 26m38.4°
4AH Scorpii1,411±124106017h 12m-32.4°
5W Cephei1,329.62163081.6722h 37m58.4°
6Westerlund 1 W2371,241±70850016h 47m-45.9°
7BC Cygni1,230.27–1,140±228271820h 22m37.6°
8IRC -10414~1,200652318h 23m-13.7°
9PZ Cassiopeiae1,190±238(–1,940±388)18120.1923h 45m61.9°
10V1489 Cygni (NML Cygni)1,183525020h 46m40.1°
11GCIRS 71,170±60–1,368unknown17h 45m-29.0°
12Westerlund 1 W26 (Westerlund 1 BKS AS)1,165±58–1,221±1201150016h 47m-45.8°
13RW Cephei1,157.92274122h 24m56.1°
14RT Carinae1,090±218143110h 45m-59.5°
15V396 Centauri1,070±214 – 1,145.317389.29 13h 18m61.7°
16V602 Carinae1,050±16513211h 14m-60.2°
17IM Cassiopeiae1,039.4328861h 33m62.4°
18CK Carinae1,013.42 – 1,060±21252610h 25m-60.3°
19KW Sagittarii994.794 – 1,009±142620017h 53m-28.0°
20UW Aquilae946.28515018h 58m-0.5°
21AZ Cephei944.22114267.8622h 9m59.7°
22CD Hydri92021981h 36m-76.3°
23CL Carinae919.78721310h 54m -61.2°
24AZ Cygni911+5729420h 58m46.5°
25NSV 25875891unknown22h 19m59.9°

Further information

The video below, made by the famous youtube channel “Kurzgesagt – In a Nutshell”, takes a deeper look into the different sizes of stars and compares them to each other.

Tanya C Forde

Written by Tanya C. Forde

Hi! I’m Tanya C. Forde, MSc (earth sciences). I was raised under the dark sky of rural Alberta and have been fascinated by astronomy since childhood. I began my exploration of the night sky with naked-eye viewing before moving on to binoculars and then telescope ownership. I also write for Sewn By Tanya.

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