Protoplanetary disc. Protoplanetary discs are compressed circles, spirals or ellipses of gas and dust, which form around protostars in the early stages of their development. Dust within a disc coalesces into planetesimals and the seeds of planets are formed. This disc is called AS 209, and its substructures are particularly pronounced thanks to its thin, high-contrast rings and almost face-on orientation towards us. Studying young star systems as they form and evolve may help us to understand more about how our Solar System formed. Image obtained by the Atacama Large Millimeter/submillimeter Array (ALMA).