Molecular clouds reveal secrets of star formation on the outskirts of galaxies Although the process of star formation inside galaxies is well understood, until now little was known about how newborn stars form and evolve at the edges of galaxies. On January 8, astronomers attending the 243rd Annual Meeting of the American Astronomical Society announced that they had observed for the first time the molecular clouds that lead to star formation in these distant regions.

About 18 years ago, the GALEX satellite discovered many newborn stars at the edge of the galaxy, an unexpected discovery. Astronomers began to wonder about the conditions for this star formation and looked for molecular clouds to be the source of star formation, but until recently they were unable to detect them in distant regions. Typically, star formation begins with the gravitational pull of a thin atomic gas that begins to condense over time. As the density of the gas increases, the atoms begin to form molecules, and the molecular gas becomes the medium that can form stars. When the GALEX satellite discovered a newborn star at the edge of her M83 galaxy in 2005, researchers were unable to detect an accompanying molecular cloud, causing controversy. Researchers used a variety of instruments, including the Atacama Large Millimeter/Submillimeter Array (ALMA), Very Large Array (VLA), Green Bank Telescope (GBT), and Subaru Telescope, to elucidate this phenomenon. Additional observations were made. They found that the outer shells of the molecular clouds at the edges of the M83 galaxy are invisible, and that observations can only detect small “cores” of these clouds.

A team of astronomers has discovered 23 individual molecular clouds in a small region of galaxy M83. This confirms the existence of star-forming regions at the edges of galaxies, but these look completely different compared to the inner regions of galaxies. Scientists believe these new observations will solve an 18-year-old mystery about how stars form at the edges of galaxies. But the study also raised new questions. In areas where molecular clouds were discovered, researchers were able to detect unusually high concentrations of atomic gases that did not correspond to the amount of molecular gas observed. New research is needed to understand the causes of this unusual phenomenon.