Star Diameter Comparison (Cited KM Figures)
Compare 13 star diameters: Proxima 200000, Sun 1392700, Pollux 12000000, Arcturus 35000000, UY Scuti 2380000000. Widely cited figures in km in one table.
Visual comparison
All values
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| Name | Value | Context | Source |
|---|---|---|---|
| Proxima Centauri 200000 km. Smallest row here. | 200,000 kilometers | M5.5 red dwarf | Observatory summaries: Proxima 0.15 solar radii |
| Sun 1392700 km. Twice 695700 radius. | 1,392,700 kilometers | G2V main sequence star | NASA NSSDC Sun Fact Sheet: radius 695700 km |
| Alpha Centauri A 1700000 km. Sun like neighbor. | 1,700,000 kilometers | G2V main sequence star | Observatory summaries: Alpha Cen A 1.22 solar radii |
| Sirius A 2380000 km. | 2,380,000 kilometers | A1V main sequence star | Observatory summaries: Sirius A 1.71 solar radii |
| Vega 3760000 km. Mean disk average. | 3,760,000 kilometers | A0V rapid rotator, oblate | Observatory summaries: Vega 2.7 solar diameters |
| Pollux 12000000 km. | 12,000,000 kilometers | K0III giant | Observatory summaries: Pollux 8.8 solar radii |
| Arcturus 35000000 km. | 35,000,000 kilometers | K1.5III giant | Observatory summaries: Arcturus 25.4 solar radii |
| Aldebaran 61000000 km. Range noted. | 61,000,000 kilometers | K5III giant | Observatory summaries: Aldebaran 44 solar radii |
| Rigel 100000000 km. Approximate. | 100,000,000 kilometers | B8Ia blue supergiant | Observatory summaries: Rigel 70 to 79 solar radii |
| Antares 800000000 km. Approximate. | 800,000,000 kilometers | M1.5Iab red supergiant | Observatory summaries: Antares 800 million km |
| Betelgeuse 900000000 km. Variable. | 900,000,000 kilometers | M1-M2Iab red supergiant | Observatory summaries: Betelgeuse 900 million km |
| VY Canis Majoris 1975000000 km. Approximate. | 1,975,000,000 kilometers | M4-M5Ia red hypergiant | Stellar studies: VY CMa 1420 solar radii |
| UY Scuti 2380000000 km. Highly approximate. | 2,380,000,000 kilometers | M4Ia red supergiant | Press summaries 2012-2015: UY Scuti 1708 solar radii |
About this converter
Star diameters span four orders of magnitude, read here in km with solar radii beside. Proxima Centauri opens near 200000 as a red dwarf anchor. The Sun reads 1392700 from twice its 695700 radius. Alpha Centauri A reads near 1700000. Sirius A reads near 2380000. Vega reads near 3760000 as an oblate rotator. Pollux reads near 12000000. Arcturus reads near 35000000. Aldebaran reads near 61000000. Rigel reads near 100000000 as an approximate blue supergiant. Antares reads near 800000000. Betelgeuse reads near 900000000 and varies with pulsation. VY Canis Majoris reads near 1975000000. UY Scuti tops the table near 2380000000 with Gaia reassessments pointing smaller. One UY Scuti spans about 1708 Suns. Supergiant edges stay fuzzy, so rows flag approximations.
How to use it
Pick two stars and a unit in the top row. The three boxes below stay linked. Change any box and the other two update. Try 1 UY Scuti against Suns to see how many home stars one hypergiant spans.
Main sequence and giant figures convert stably from solar radii, while supergiant studies spread wide and stay flagged per row. Vega oblateness and Betelgeuse dimming events ride in notes. UY Scuti rows pin the 1708 radii press figure against smaller Gaia reassessments. Canopus, Deneb and Stephenson 2-18 stay out for lack of single stable figures.
FAQ
What is the biggest star here?
Near 2380000000 km from 1708 solar radii in 2012 to 2015 press work. Gaia reassessments point smaller near 1300000000, and the row pins both.
How big is the Sun?
1392700 km from twice the 695700 km NASA radius. One UY Scuti spans about 1708 Suns.
What is the smallest here?
Near 200000 km as the red dwarf anchor. Interferometry points near 214000, and the row pins the rounded figure.
Are giant figures exact?
Yes for supergiants. Fuzzy edges, winds and pulsation spread studies, so rows flag Antares, Betelgeuse, VY CMa and UY Scuti as approximate.
Sources
- NASA NSSDC Sun Fact Sheet (radius 695,700 km)
- SIMBAD Astronomical Database stellar radii (cross checks)
- University observatory star pages (Sirius, Vega, Arcturus, Aldebaran, Pollux, Rigel, Antares, Betelgeuse)
- Peer reviewed interferometry papers (Arcturus, Aldebaran, Antares, Betelgeuse, VY CMa, UY Scuti)
Last verified: 2026-10-01 · 13 entries
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