# Mid-infrared Imaging of SR 12 c with JWST/MIRI: Grain Growth in an Evolved Circumplanetary Disk

**Authors:** Ya-Lin Wu, Claire O. Finley, Brendan P. Bowler, Ning Chen, Yuhiko Aoyama, Gregory J. Herczeg, Catherine C. Espaillat, William Best, Ian Czekala, Katherine B. Follette, Adam L. Kraus, Raquel A. Martinez, Connor E. Robinson, Quang H. Tran, Kimberly Ward-Duong, Yifan Zhou  
**arXiv:** [2610.24776](https://arxiv.org/abs/2610.24776)  
**Date:** 2026-10-17  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2610.24776v1/

## Key points

- The study examines the circumplanetary dust disk around SR 12 c, a planetary-mass companion approximately 1,200 astronomical units from SR 12 AB.
- JWST/MIRI imaging at 5.6–21 micrometers is combined with infrared-to-submillimeter data, including ALMA observations, to investigate disk structure, heating, and dust properties.
- Two blackbody components are needed to describe the emission, suggesting a range of temperatures and emitting areas rather than proving two separate disks.
- Physical models favor a compact, predominantly flat disk heated mainly by irradiation, with a smaller contribution from viscous dissipation.
- The inferred inner radius is approximately three Jupiter radii; the outer radius is around three astronomical units but is poorly constrained.
- The lack of strong excess emission near 10 micrometers suggests substantial grain growth and dust settling, consistent with an evolved disk, but does not directly measure grain sizes.
- SR 12 c broadly follows empirical star–disk scaling relations, although its formation pathway remains uncertain.
- Only the title, author list, and abstract were available, limiting assessment of methods, parameter uncertainties, and alternative models.

## Summary

The paper investigates the structure and physical properties of the dust disk around SR 12 c, a planetary-mass companion located approximately 1,200 astronomical units from the binary system SR 12 AB. Circumplanetary disks offer clues to the formation of giant planets and their satellites. SR 12 c is a particularly useful target because its dust disk has already been directly detected with the Atacama Large Millimeter/submillimeter Array (ALMA). This study adds mid-infrared observations to investigate the disk’s temperature distribution, geometry, heating mechanisms, and dust properties. Only the paper’s title, author list, and abstract are available here. This summary therefore cannot evaluate the observations, modeling methods, or uncertainties beyond what the abstract explicitly reports. The authors present imaging obtained with the Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST), spanning wavelengths from 5.6 to 21 micrometers. They combine these observations with infrared-to-submillimeter data to construct and interpret the system’s spectral energy distribution, which describes how its emission varies with wavelength. This broad wavelength coverage connects emission from warmer material, prominent in the infrared, with the cooler dust traced at submillimeter wavelengths. The analysis uses both a simple descriptive representation of the emission and physically motivated disk models that explore different geometries and heating mechanisms. The descriptive model represents the disk emission with two blackbody components that have markedly different characteristic temperatures and radii. This suggests that a single temperature and emitting area cannot adequately reproduce the observed emission. However, the abstract does not specify the components’ temperatures or radii, and the two-component fit alone does not establish the presence of two physically separate disks. The physical models favor a predominantly flat disk heated mainly by irradiation, with a smaller contribution from viscous dissipation. The inferred disk is compact, with an inner radius of approximately three Jupiter radii. Its outer radius is less certain: the authors report a characteristic value of about three astronomical units but describe it as loosely constrained. The modeling thus provides a clearer estimate of the inner boundary than of the disk’s overall radial extent. Another important finding is the absence of strong excess emission near 10 micrometers. The authors interpret this as evidence of substantial grain growth and dust settling, consistent with an evolved circumplanetary disk. They also find that SR 12 c broadly follows empirical star–disk scaling relations. This places the planetary-mass system in the wider context of disks around stars and may help inform its formation history, although the abstract does not establish a unique formation pathway. Overall, the study highlights the value of combining JWST mid-infrared imaging with ALMA submillimeter observations to investigate circumplanetary disks. The results support a picture of a compact, largely flat disk heated primarily by irradiation and containing substantially evolved dust. Important limitations remain: the outer radius is poorly constrained, the interpretation of dust evolution is not a direct measurement of grain sizes, and the abstract provides neither detailed parameter uncertainties nor model comparisons. The findings therefore support a coherent physical interpretation without uniquely determining the disk’s structure or formation history.