NASA's Webb reveals cathedral of massive stars in Pismis 24 Cluster, brightest not alone

NGC 6357: Cathedral to Massive Stars (Image: NASA)

Astronomers have long wondered how massive a normal star can be. Observations from the Webb Space Telescope have now provided fresh insights. A star in the Pismis 24 cluster was once thought to be over 200 times the Sun’s mass. This would have made it one of the most massive stars ever recorded.

Pismis 24-1: A Trio, Not a Single Star

The brightest object in the cluster lies near the central cavity. Infrared images from Webb reveal its brilliance comes from at least three stars. Each of these stars still measures close to 100 solar masses. Their combined luminosity had previously led astronomers to overestimate a single star’s size. Visible light images from the Hubble Space Telescope provide a comparison of the cluster.

NGC 6357 (Image: NASA/ESA/CSA/STScI/Alyssa Pagan/JWST)

Stellar Formation in NGC 6357

Toward the bottom of the image, new stars are still forming. These stars emerge within the emission nebula NGC 6357, which surrounds Pismis 24. Central energetic stars illuminate a spectacular cocoon of gas and dust. Their action is reminiscent of the soaring arches of a Gothic cathedral. Webb's observations underscore the intricate dynamics of star birth within the huge clusters.

These observations provide a more nuanced understanding of how the most massive stars form. They also demonstrate that extreme brightness does not necessarily mean one large giant star. Webb continues to reveal secrets of stellar nurseries not previously known.