Free Astronomy Magazine January-February 2024

38 JANUARY-FEBRUARY 2024 ASTRO PUBLISHING ics of supermassive black holes. At the centers of many massive galax- ies, there exist “supermassive black holes” with masses exceeding a mil- lion times that of the Sun. How are these supermassive black holes formed? One of the crucial growth mechanisms proposed by previous research is “gas accretion” onto the black hole. This refers to how gas in the host galaxy somehow falls to- ward the central black hole. The gas that gathers very close to su- permassive black holes is accelerated at high speeds due to the gravity of the black hole. Due to intense fric- tion between gas particles, this gas heats up to several million degrees and emits brilliant light. This phe- nomenon is known as an active galactic nucleus (AGN), and its brightness can sometimes surpass the combined light of all the stars in the galaxy. Interestingly, a portion of the gas that falls towards the black hole (accretion flow) is thought to be blown away by the immense energy of this active galac- tic nucleus, leading to outflows. Both theoretical and observational studies have provided detailed in- sights into gas accretion mechanisms from the 100,000 light-year scale of the galaxies down to a scale of a few hundred light-years at the center. However, the gas accretion within by ALMA Observatory Bárbara Ferreira I n a scientific breakthrough, an in- ternational team of scientists has delved into the heart of the Circi- nus Galaxy’s active galactic nucleus using the Atacama Large Millime- ter/submillimeter Array (ALMA). Achieving an unprecedented resolu- tion of about one light-year, the re- search has illuminated the intricate dance of gas flows around the galaxy’s supermassive black hole, en- compassing plasma, atomic, and mo- lecular phases. Notably, the team has elucidated the accretion flow — driven by a mechanism termed “gravitational instability”— that feeds the black hole. Intriguingly, not all this gas contributes to the black hole’s growth. A significant fraction is ejected as atomic or mo- lecular outflows, only to return and again be drawn towards the black hole in a cyclical pattern reminiscent of a water fountain. This profound discovery paves the way for a more holistic grasp of the growth dynam- Gas recycling process near a supermassive black hole unveiled