Free Astronomy Magazine July-August 2025

16 ASTRO PUBLISHING cule commonly found in interstellar gas clouds and widely used industri- ally on Earth, as a tracer to map the gas dynamics around the star. Observations revealed a dense ring of hot ammonia gas spanning radii of 200 to 700 astronomical units (AU) around HW2. This structure was identified as part of an accre- tion disk—a key feature in star for- mation theories. The study found that gas within this disk is both collapsing inward and rotating around the young star. Re- markably, the infall rate of material onto HW2 was measured at two thousandths of a solar mass per year—one of the highest rates ever observed for a forming massive star. These findings confirm that accre- tion disks can sustain such extreme mass transfer rates even when the central star has already grown to 16 times the mass of our Sun. JULY-AUGUST 2025 U sing the U.S. National Science Foundation National Radio Astronomy Observatory’s (NSF NRAO) U.S. National Science Founda- tion Very Large Array (NSF VLA), as- tronomers have revealed for the first time the huge flow of gas near a massive star in the making which al- lows its rapid growth. By observing the young star HW2 in Cepheus A, located 2300 light years from Earth, researchers have resolved the struc- ture and dynamics of an accretion disk feeding material to this massive star. This finding sheds light on a central question in astrophysics: how do massive stars, which often end their lives as supernovae, accumu- late their immense mass? Cepheus A is the second closest site of massive star formation to Earth, making it an ideal laboratory for studying these challenging processes. The research team used ammonia (NH 3 ), a mole- Unveiling the birth secrets of HW2 in Cepheus A by National Radio Astronomy Observatory