Pismis 24: War and Peace Nebula
Pismis 24-1 (also known as HDE 319718) is part of the open cluster Pismis 24 within the nebula NGC 6357 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. Pismis 24-1 is composed of at least three objects, the resolved Pismis 24-1SW and the unresolved spectroscopic binary Pismis 24-1NE.
The combined Pismis 24-1NE is slightly more luminous and hotter than 24-1SW, but is likely to consist of two similar objects both less luminous. This is surprising given the spectral luminosity classes and it could be that the interaction between the components of 24-1NE is confusing its classification.
When originally discovered and thought to be a single star, Pismis 24-1 was calculated to have a mass around 300 times the sun, but as currently known all three components have masses less than 100 times the sun.
NGC 6357 is a diffuse nebula near NGC 6334 in the constellation Scorpius. The nebula contains many proto-stars shielded by dark disks of gas, and young stars wrapped in expanding “cocoons”.
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 looks like a skull.
This nebula includes the open cluster Pismis 24, which is home to several massive stars. One of the brightest stars in the cluster, Pismis 24-1, was thought possibly to be the most massive on record, approaching 300 solar masses, until it was discovered to be a binary system with each star exceeding 100 solar masses.