# JWST-TST High Contrast: Medium-resolution spectroscopy reveals a carbon-rich circumplanetary disk around the young accreting exoplanet Delorme 1 AB b

**Authors:** Mathilde Mâlin, Kimberly Ward-Duong, Sierra L. Grant, Nicole Arulanantham, Benoît Tabone, Laurent Pueyo, Marshall Perrin, William O. Balmer, Sarah Betti, Christine H. Chen, John H. Debes, Julien H. Girard, Kielan K. W. Hoch, Jens Kammerer, Cicero Lu, Isabel Rebollido, Emily Rickman, Connor Robinson, Kadin Worthen, Roeland P. van der Marel  
**arXiv:** [2510.07253](https://arxiv.org/abs/2510.07253)  
**Date:** 2025-10-08  
**Summary page:** https://www.summarizepaper.com/en/paper/2510.07253v1/

## Key points

- Researchers used the James Webb Space Telescope (JWST) for medium-resolution spectroscopic observations of the young accreting exoplanet Delorme 1 AB b.
- Delorme 1 AB b is estimated to be between 30-45 million years old and draws material from a circumplanetary disk (CPD) consisting of gas and dust.
- Observations aimed to investigate circumplanetary material, atmospheric properties, and composition through sophisticated forward modeling using atmospheric models.
- Spectral energy distribution (SED) beyond 10 microns is dominated by emissions from the CPD rather than from the planet itself.
- Emission signals of hydrogen cyanide (HCN) and acetylene (C$_2$H$_2$) were detected within the CPD spectrum, with an elevated carbon-to-oxygen ratio observed.
- Spatially extended hydrogen gas (H$_2$) emission around the planet suggests warm gas at potentially higher temperatures compared to other components.
- Bright emissions of carbon-bearing species within the CPD, indications of an outflow traced by extended H$_2$ emissions, and hot dust continuum emissions hinting at an inner cavity were revealed in the mid-infrared spectrum.
- These findings provide crucial constraints on both the chemical composition and physical conditions of Delorme 1 AB b's circumplanetary disk.

## Summary

Researchers have utilized the James Webb Space Telescope (JWST) to conduct medium-resolution spectroscopic observations of the young accreting exoplanet Delorme 1 AB b. This planetary-mass companion is estimated to be between 30-45 million years old and is believed to draw material from a circumplanetary disk (CPD) consisting of gas and dust. The team's observations with JWST/MIRI aimed to investigate the presence of circumplanetary material around this intriguing planet and characterize its atmospheric properties and composition through sophisticated forward modeling using atmospheric models. One striking finding is that beyond 10 microns, the spectral energy distribution (SED) is dominated by emissions from the CPD rather than from the planet itself. The researchers detected robust emission signals from hydrogen cyanide (HCN) and acetylene (C$_2$H$_2$) within the CPD spectrum. Interestingly, no oxygen-bearing species were observed in this region, indicating an elevated carbon-to-oxygen ratio in the gas surrounding Delorme 1 AB b. Moreover, spatially extended hydrogen gas (H$_2$) emission was identified around the planet, suggesting warm gas at potentially higher temperatures compared to other components. The mid-infrared spectrum also revealed bright emissions of carbon-bearing species within the CPD and indications of an outflow traced by extended H$_2$ emissions that could signify a disk wind phenomenon. Additionally, hot dust continuum emissions hinted at an inner cavity within the CPD structure. These findings provide crucial constraints on both the chemical composition and physical conditions of Delorme 1 AB b's circumplanetary disk. , , , , 

By studying these long-lived "Peter Pan" disks associated with planetary-mass objects like this one, researchers can deepen their understanding of how accretion mechanisms persist in evolved low-mass systems over time. This research sheds light on important aspects related to planetary system formation, longevity, and evolutionary pathways—offering new avenues for further exploration and discovery in this fascinating field of study.