Free Astronomy Magazine January-February 2020

32 JANUARY-FEBRUARY 2020 SPACE CHRONICLES ALMA witnesses planet formation in action by ALMA Observatory F or the first time, astronomers using the Atacama Large Mil- limeter/submillimeter Array (ALMA) have witnessed 3D motions of gas in a planet-forming disk. At three locations in the disk around a young star called HD 163296, gas is flowing like a waterfall into gaps that are most likely caused by planets in formation. These gas flows have long been predicted and would di- rectly influence the chemical compo- sition of planets atmospheres. A rtist’s impression of gas flow- ing like a waterfall into a pro- toplanetary disk gap, which is most likely caused by an infant planet. [NRAO/AUI/NSF, S. Dagnello]