Astronomers using the Atacama Large Millimeter/submillimeter Array have detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding a young star called Elias 2-27. This spiral feature was produced by density waves — gravitational perturbations in the disk. ALMA peered into the Ophiuchus star-forming region to study the protoplanetary disk around Elias 2-27. Image credit: L. Pérez / B. Saxton / MPIfR / NRAO / AUI...
