Pismis 24-1
Encyclopedia
Pismis 24-1 is part of the open cluster Pismis 24 within the nebula
Nebula
A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...

 NGC 6357
NGC 6357
NGC 6357 is a diffuse nebula near NGC 6334 in the constellation Scorpius. This nebula was given the name War and Peace Nebula by the Midcourse Space Experiment scientists because of its appearance. They said that in infrared images the bright, western part resembles a dove, while the eastern part...

 about 8150 light-years away. Pismis 24-1 is the largest and more brilliant of the visible stars of this cluster, and is one of the most massive and luminous stars known. The star is at least a triple star, as revealed by the recent observation of camera ACS of the Hubble space telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...

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Pismis 24-1 is composed of at least three objects, the resolved Pismis 24-1SW and the unresolved spectroscopic binary Pismis 24-1NE. Pismis 24-1SW is a very bright blue supergiant
Blue supergiant
Blue supergiants are supergiant stars of spectral type O or B.They are extremely hot and bright, with surface temperatures of 30,000-50,000 K. They typically have 10 to 50 solar masses on the Hertzsprung-Russell diagram, and can have radii up to about 25 solar radii...

, which probably is about to become a luminous blue variable
Luminous blue variable
Luminous blue variables, also known as S Doradus variables, are very bright, blue, hypergiant variable stars named after S Doradus, the brightest star of the Large Magellanic Cloud. They exhibit long, slow changes in brightness, punctuated by occasional outbursts in brightness during substantial...

. The evolutionary zero-age masses of those two objects and that of the nearby Pismis 24-17 are all approximately 100 solar masses, very large but under the stellar upper mass limit
Eddington luminosity
The Eddington luminosity in a star is defined as the point where the gravitational force inwards equals the continuum radiation force outwards, assuming hydrostatic equilibrium and spherical symmetry. When exceeding the Eddington luminosity, a star would initiate a very intense continuum-driven...

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