UY Scuti

UY Scuti is a red supergiant variable star in the constellation Scutum. Its estimated radius places it among the largest known stars, though measurements remain uncertain.

Red supergiant: A massive, evolved star with a cool surface and an expanded outer envelope. UY Scuti belongs to this stellar class.
Stellar evolution: The changes in a star’s structure and composition over its lifetime. UY Scuti’s enormous size reflects a late stage in stellar evolution.
Betelgeuse: A nearby red supergiant in Orion whose changing size and brightness are studied in detail. Its better-resolved surface offers a useful comparison with UY Scuti’s uncertain dimensions.
Parallax: The apparent shift in an object's position caused by observing it from different locations. Distance uncertainty propagates directly into estimates of UY Scuti’s luminosity and radius.
Stellar radius: The distance from a star’s center to the outer boundary used to define its size. Estimates of this quantity place UY Scuti among the largest known stars.
Hydrostatic equilibrium: The balance between inward gravity and outward pressure in a stable astronomical object. This balance governs the star’s structure while its outer layers expand.
VY Canis Majoris: A red hypergiant in Canis Major known for its extensive circumstellar material. It is another candidate for the largest stellar radii.
Interferometry: A method that combines waves from multiple telescopes to achieve finer angular resolution. It can help measure the angular diameter of a distant, unresolved star.
Stellar luminosity: The total energy a star emits per unit time across all wavelengths. Its luminosity helps astronomers infer UY Scuti’s radius and distance.
Stellar pulsation: Periodic expansion and contraction of a star caused by changes in its internal pressure and energy flow. Pulsation contributes to changes in UY Scuti’s brightness and radius.

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