JERUSALEM, Feb. 4 (Xinhua) -- An international team of scientists has for the first time measured the effect of cosmic rays inside a star-forming nebula, the Israel Institute of Technology said in a statement on Wednesday.
Stars and planets form in cold, dense clouds of gas and dust, where cosmic rays are the dominant source of ionization and heating.
Cosmic rays are high-energy particles, including protons, electrons, and atomic nuclei, that move near light speed and help drive star formation.
Scientists have been using the cosmic-ray ionization rate, the rate at which cosmic rays ionize molecular hydrogen per second, to describe the chemical, physical, and thermal state of star-forming regions.
In previous studies, astronomers observed ionization primarily through chemical line observations and models. This roundabout approach may lead to highly variable results.
In the latest research published in Nature Astronomy, the team observed nebula Barnard 68 with James Webb Space Telescope, measuring extremely faint infrared lines that arise when cosmic rays directly excite the gas. Astronomers have theorized about these directly excited lines for decades, yet direct observations remain elusive.
The team led by the Israel Institute of Technology detected a faint glow of directly stimulated molecular hydrogen. It is the first time that cosmic rays are observationally confirmed to stimulate measurable infrared lines directly.
The researchers said their study opens a transformative observational window into the origin, propagation and role of cosmic rays in star formation and galaxy evolution. They have been approved to use James Webb Space Telescope to study another cloud. ■
