Limits RegistryPUBLIC RECORD
Limits RegistryStephenson 2-18, a red hypergiant roughly 20,000 light-years away in the Stephenson 2 cluster, has a commonly cited estimated radius of around 2,150 times the Sun's — large enough that, placed at the Sun's position, its surface would reach past Saturn's orbit. The exact figure is genuinely disputed and highly sensitive to the assumed distance and luminosity; UY Scuti (estimates spanning roughly 1,000-1,700 solar radii) is a frequently cited rival, and neither star has the direct interferometric size measurement available for closer, smaller stars.
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Stephenson 2-18, a red hypergiant roughly 20,000 light-years away in the Stephenson 2 cluster, has a commonly cited estimated radius of around 2,150 times the Sun's — large enough that, placed at the Sun's position, its surface would reach past Saturn's orbit. The exact figure is genuinely disputed and highly sensitive to the assumed distance and luminosity; UY Scuti (estimates spanning roughly 1,000-1,700 solar radii) is a frequently cited rival, and neither star has the direct interferometric size measurement available for closer, smaller stars.
The largest stellar radius estimated for any currently known star, in multiples of the Sun's radius, based on luminosity and temperature modeling.
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Permanent ID limitsregistry.com/limits/LR-LARGEST-STAR-RADIUS
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Limits Registry. LR-LARGEST-STAR-RADIUS. Largest known star by radius. 2026.