Spiral Density Waves in a Young Protoplanetary Disk

TL;DR

This study uses ALMA observations to detect and analyze spiral density waves in the midplane of a young protoplanetary disk, providing insights into disk structure and planet formation processes.

Contribution

First direct detection of spiral density waves in the disk midplane of a young star using millimeter observations, confirming theoretical predictions.

Findings

Detected symmetric spiral arms extending to the disk outer regions.

Observed an emission gap closer to the star than the spiral arms.

Spiral arms trace shocks of density waves in the disk midplane.

Abstract

Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed spiral structure were not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. Using the Atacama Large Millimeter/submillimeter Array we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. The arms extend to the disk outer regions and can be traced down to the midplane. These millimeter-wave observations also reveal an emission gap closer to the star than the spiral arms. We argue that the observed spirals trace shocks of spiral density waves in the midplane of this young disk.