Shadows in the protoplanetary disk around HD 142527 reveal dust grain sizes

Star system: HD 142527 | Distance from the Sun: 519 light years

Planet formation begins within protoplanetary disks, which are swirling clouds of gas and dust surrounding young stars. To understand how planets emerge, it is critical to determine the size of dust grains within these disks. A new method has been developed to estimate these sizes by measuring how quickly different regions of a disk cool down. This technique specifically analyzes transitional disks where an inner disk is tilted, casting a distinct shadow across the outer disk.

The research focuses on the disk surrounding the young star HD 142527. By comparing images of scattered near-infrared light with submillimeter maps of dust, the offset between sunlight-irradiated regions and shadowed regions was used to calculate the cooling timescale. An analytic model was then applied to connect these cooling rates to the physical properties of the dust and the intensity of turbulence within the disk material.

The analysis shows that the northern shadow cast on the disk of HD 142527 cools on a timescale lasting only a few percent of its total orbital period. Based on this, the maximum size of dust grains is estimated to be between 0.1 and 1 millimeter. These findings also confirm that the environment is suitable for a phenomenon called vertical shear instability, a type of turbulence that helps regulate how material moves within the disk.

Key findings
- Cooling timescales in the HD 142527 disk were successfully derived from shadow patterns.
- Maximum dust grain size in the northern shadowed region is estimated at 0.1 to 1 millimeter.
- Short cooling times support the presence of vertical shear instability within the disk.
- Observed turbulence levels align with predictions based on near-infrared imaging.

Scientific study

Probing disk dynamics and dust evolution through shadows in protoplanetary disks: A case study of the HD 142527 disk (external link)