Most stars form in clusters, including massive stars that emit high-energy radiation, disrupting the dust and gas needed for planet formation. A team of astronomers used NASA’s Chandra X-ray Observatory and other data to identify hazardous areas in the Cygnus OB2 star cluster, the nearest large cluster to our Sun at about 4,600 light-years away.
Their observations mapped X-ray emissions and cataloged young stars, creating a detailed cluster image. Chandra’s data highlights the X-ray glow and young stars, while infrared data from the Spitzer Space Telescope shows cooler dust and gas, providing a comprehensive view of the star-forming environment.
In the new composite image of Cygnus OB2, Chandra’s data (in purple) highlights diffuse X-ray emissions and young stars, while infrared data from the Spitzer Space Telescope (in red, green, blue, and cyan) reveals cooler dust and gas.
In these dense star clusters, high-energy radiation from massive stars and planets can severely affect forming planetary disks. Over time, these disks fade as some material falls onto the star, while the rest is heated and evaporates due to X-rays and ultraviolet light. This evaporation process, known as “photoevaporation,” typically takes 5 to 10 million years for average-sized stars. However, nearby massive stars can speed up this process significantly.
Researchers found that planet-forming disks around stars vanish much faster near massive stars emitting high-energy radiation. In more crowded regions of Cygnus OB2, the fraction of young stars with disks drops from about 40% in less intense areas to around 18% in regions with high radiation and more stars. The most dangerous zone for forming planetary systems is within about 1.6 light-years of the most massive stars.
Additionally, a separate study by the same team revealed that the higher-energy X-ray emissions in the cluster result from gas winds from massive stars colliding, heating the gas, and generating X-rays. In contrast, less energetic emissions likely come from gas colliding with the surrounding cluster gas.