Late infall triggers asymmetric carbon chemistry in HD 142527’s planet-forming disk

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

HD 142527’s planet-forming disk is famous for its asymmetric dust trap, shadows, and spiral arms. Using new ALMA observations, researchers mapped a wide range of molecules and found that emissions from H₂CO, CN, and C₂H are concentrated in spiral-like features in the southern disk, opposite the dust trap. These features are not linked to the disk’s shadows but are likely caused by late infall of carbon-rich material, which boosts the local carbon-to-oxygen ratio and enhances gas-phase chemistry.

Other molecules, like C¹⁷O and HCO⁺, are found near the dust trap, probably due to higher surface density there. Differences in C¹⁷O transitions may be due to dust obscuration. The four observed CS transitions trace both a cold, ring-like reservoir and a hotter region influenced by infalling material. A weak SO signal may result from shocks in the spiral arms. Overall, the study shows that late infall of material can drive asymmetric chemistry in planet-forming disks.

Key findings
- Emissions from H₂CO, CN, and C₂H are concentrated in spiral features, not linked to shadows.
- Late infall of carbon-rich material enhances local chemistry.
- C¹⁷O and HCO⁺ emissions are associated with the dust trap.
- CS traces both cold and hot reservoirs; SO may be shock-induced.

Scientific study

The asymmetric carbon-rich chemistry of the planet-forming disk of HD 142527 triggered by late infall (external link)