Brown dwarfs have fascinated astronomers for decades: too massive to be planets but not massive enough to shine like stars, their origins remain a subject of debate. Do they form like stars through the gravitational collapse of gas clouds, or are they more like giant planets that have acquired extraordinary amounts of matter? A CNRS Earth and Universe research team has just simulated for the first time the complete birth of a brown dwarf through gravitational collapse, revealing the physical properties of these mysterious objects in their early stages.

To achieve this result, the researchers used the RAMSES calculation code on French supercomputers at TGCC and CBPsmn. These cutting-edge 3D simulations incorporate all the key physical elements: gravity, radiation, and magnetic fields, interacting at different spatial and temporal scales. The team modeled the collapse of dense cores with low mass (0.05 to 0.1 solar mass) over a considerable dynamic range, with 8 orders of magnitude in spatial extent (1,000 astronomical units to a few thousand kilometers) and 17 orders of magnitude in density (10^5 to 10^22 particles per centimeter^3). This self-consistent approach makes it possible to follow the entire sequence: isothermal collapse, formation of the first hydrostatic core, dissociation of molecular hydrogen H₂, and finally the birth of the brown dwarf.

Read more on the CNRS website (in French)

Reference

Ahmad, A. A., Commerçon, B., Chabrier, G., & Borderies, A. (2025). Brown Dwarf Formation Through Gravitational Collapse: Insights From 3D Numerical Simulations. Astrophysical Journal.
DOI: 10.3847/2041-8213/ae0640