Astronomers believe that the star’s exceptionally high mass may be linked to its location near the Milky Way centre. At the time of discovery, the Pistol Star was suspected to have been the most massive star known before it had started shedding material, possibly exceeding the theoretical upper limit, with an initial mass of up to 200 solar masses. The Pistol Star was discovered by Don Figer, an astronomer at UCLA, using the Hubble Space Telescope in the 1990s. The star radiates the same amount of energy in 20 seconds as our Sun does in a year. The star’s radius is 306 times solar and its stellar wind is more than 10 billion times stronger than our Sun’s. The star’s current mass is uncertain but, based on its spectrum, it is estimated to be 27.5 solar masses. When the star formed, it likely had a mass more than 100 times solar, but now has a lot less as a result of ejecting a vast amount of material. The Pistol Star is believed to have shed almost 10 solar masses of material in huge outbursts between 4,000 and 6,000 years ago. Size comparison of a hypothetical quasi-star/black hole star (diameter of ~10 billion kilometers or ~7,187 solar diameters, mass of 1000+ solar masses) and several known giant stars: UY Scuti (~1708 solar diameters, ~7-10 solar masses), VY Canis Majoris (~1420 solar diameters, ~17 solar masses), Betelgeuse (~887 solar diameters, ~11.6 solar masses), the Pistol Star (~306 solar diameters, ~27.5 solar masses), Rigel (~78.9 solar diameters, ~23 solar masses), and R136a1 (~35.4 solar diamaters, ~265 solar masses). Without the interstellar dust and the surrounding nebulosity, the Pistol Star would be visible to the unaided eye, shining at 4th magnitude from a distance of 25,000 light years. It is a member of the Quintuplet Cluster and, like many other exceptionally massive and luminous stars in the cluster, it cannot be seen visually because it is obscured by the dust in the region of the Milky Way’s core.

The Pistol Star is the central star in the Pistol Nebula and was named after the nebula’s shape. Its absolute bolometric magnitude is -10.75. The Pistol Star’s surface temperature is 11,800 K. It is a candidate luminous blue variable (cLBV) and one of the most luminous stars known, with a luminosity 1,600,000 times that of the Sun.Įarly observations indicated that it was the single most luminous star known, with an estimated luminosity almost 10 million times solar, but later studies reduced the estimate to about a third of the luminosity of Eta Carinae. The Pistol Star, also known as V4647 Sagittarii, is a blue hypergiant star located about 25,000 light years from Earth in the constellation Sagittarius.

Star pistol box