Drake etal, IR:NASA/JPL-Caltech/Spitzer; Image processing: NASA/CXC/SAO/N.
Wolk
By using the Chandra X-ray Space Telescope of the NASA and the Spitzer Space Telescope (now deactivated), a group of astronomers has identified real “danger zones” for planets in formation around young stars.
These discoveries were made possible thanks to detailed observations of the star cluster Cygnus OB2located approximately 4,600 light years of the Terre.
Cygnus OB2 is one of the largest nearby star clusters, containing hundreds of massive stars and thousands of smaller stars. The images obtained were combined to create a vast mosaicallowing scientists to highlight the luminosity of high-energy X-rays scattered among stars, thereby constructing an inventory of young, bright stars of Cygnus OB2.
This inventory has been enriched with optical and infrared data from Spitzer, allowing a complete census of the cluster to be carried out. The final composite image reveals the diffuse X-ray emissions (in purple), which delineate the young stars of Cygnus OB2, and the infrared data (in red, green, blue and cyan), which show other young stars, as well as dust and cold gas in the region.
THE large newborn stars emit intense X-rays and ultraviolet radiation, creating a hostile environment for planetary formation around nearby stars. The main risk for planets in formation in dense star clusters like Cygnus OB2 comes from the powerful radiation emitted by young massive stars.
This radiation hits the protoplanetary disks — flat, rotating clouds composed of gas and dust, which represent the material for the birth of planets — and can cause their evaporation through a process known as deposition photoévaporation.
Subsequently, the vaporized material is expelled from the star by the pressure of the radiation, creating a phenomenon called “wind of the disc”. For a star of average mass, like the Soleilphotoevaporation and disk winds take between 5 and 10 million years to completely dissolve a protoplanetary disk.
However, in regions with high concentrations of massive stars, the process can be much faster due to the intensity of ultraviolet and X-ray radiation. Data provided by telescopes Chandra et Spitzer demonstrated the acceleration of dissipation of protoplanetary disks exposed to high levels of radiation.
In particular, it was observed that this dissolution is faster in the areas of Cygnus OB2 with high stellar density.
In less dense areas of the cluster, approximately 40% young stars retain protoplanetary disks, while in more populated regions this percentage drops to 18%.
In the areas closest to the most massive stars, within a radius of approximately 1.6 light yearsthe presence of discs drops drastically to almost 1%. These “danger zones” for planetary training highlight the risks that protoplanetary disks face in dense stellar environments filled with high-energy radiation.
The conclusions of this study, published in The Astrophysical Journalalso include a complementary analysis that studied the characteristics of X-ray emissions from disk winds around massive stars.
This research further highlights how planet formation is influenced by the extreme conditions present in dense star clusters like Cygnus OB2, providing new insights into the factors that can hinder or promote the birth of planetary systems.
Our Meteo Giornale articles are on Google News, follow us for free!
Follow our feed!
