UY Scuti was first catalogued in 1860 by German astronomers at the Bonn Observatory, who were completing a survey of stars for the Bonner Durchmusterung Stellar Catalogue. It was designated BD-12°5055, the 5,055th star between 12°S and 13°S counting from 0h right ascension. On detection in the second survey, the star was found to have changed slightly in brightness, suggesting that it was a new variable star. In accordance with the international standard for designation of variable stars, it was called UY Scuti, denoting it as the 38th variable star of the constellation Scutum. UY Scuti is located a few degrees north of the A-type starGamma Scuti and northeast of the Eagle Nebula. Although the star is very luminous, it is, at its brightest, only 9th magnitude as viewed from Earth, due to its distance and location in the Zone of Avoidance within the Cygnus rift.
Characteristics
UY Sct is a dust-enshrouded bright red supergiant and is classified as a semiregular variable with an approximate pulsation period of 740 days. In the summer of 2012, AMBERinterferometry with the Very Large Telescope in the Atacama Desert in Chile was used to measure the parameters of three red supergiants near the Galactic Center region: UY Scuti, AH Scorpii, and KW Sagittarii. They determined that all three stars are over 1,000 times bigger than the Sun and over 100,000 times more luminous than the Sun. The stars' sizes were calculated using the Rosseland radius, the location at which the optical depth is, with distances adopted from earlier publications. UY Scuti was found to be the largest and the most luminous of the three stars measured, at based on an angular diameter of and an assumed distance of which was originally derived in 1970 based on the modelling of the spectrum of UY Sct. The luminosity is then calculated to be at an effective temperature of 3,365 ± 134 K, giving an initial mass of . Direct measurements of parallax of UY Sct by the Gaia Data Release 2 have recently given a parallax of, yielding a much lower distance of approximately, and consequently much lower luminosity and radius values of around and respectively. UY Scuti's mass is uncertain, primarily because it has no visible companion star by which its mass can be measured through gravitational interference. However, it is expected to be between. Mass is being lost at per year, leading to an extensive and complex circumstellar environment of gas and dust.
Supernova
Based on current models of stellar evolution, UY Scuti has begun to fuse helium, and continues to fuse hydrogen in a shell around the core. The location of UY Scuti deep within the Milky Way disc suggests that it is a metal-rich star. After fusing heavy elements, its core will begin to produce iron, disrupting the balance of gravity and radiation in its core and resulting in a core collapse supernova. It is expected that stars like UY Scuti should evolve back to hotter temperatures to become a yellow hypergiant, luminous blue variable, or a Wolf–Rayet star, creating a strong stellar wind that will eject its outer layers and expose the core, before exploding as a type IIb, IIn, or type Ib/Ic supernova.
