The ingredients available to forming planets can differ sharply even in seemingly comparable stellar nurseries. An ALMA study posted October 15 and accepted by The Astrophysical Journal compares water and organic molecules in the disks around HD 100546 and IRS 48.
Both water vapor and methanol were detected around HD 100546. Their inferred methanol-to-water column-density ratio is about 0.02, near the median measured for comets. Around IRS 48, methanol appeared but water vapor did not, placing the ratio above 0.2. Nondetection does not mean the entire disk lacks water.
The contrast continues with methyl formate: its abundance relative to methanol is approximately 0.2 in IRS 48 but about two in HD 100546. The latter may reflect chemical enhancement in the gas. These are model-dependent molecular inventories, not measurements of biological activity. The authors also examine excitation and opacity, which affect how emission translates into abundance.
Reading the material in the ice
IRS 48 already has an important chemical history. In research announced by ESO in March 2022, astronomers detected dimethyl ether in its disk. The system contains an asymmetric concentration of dust that can collect icy grains. Such grains provide surfaces where atoms and simpler molecules meet and react in cold environments.
Heating can then turn those ices into gas, making previously hidden molecules visible to radio telescopes. This offers a way to investigate material that could eventually enter comets, asteroids and planets. The older work helped establish IRS 48 as a place to follow that chemical journey, rather than merely counting molecules in isolation.
The new comparison adds a useful warning to that picture: there is no reason to assume every planet-forming disk starts with the same recipe or preserves it unchanged. Understanding the ingredients is a step toward understanding planetary environments. It is not evidence that either system has produced living organisms.
Reporting checked October 20, 2026 (UTC). Catch-up coverage of the October 15 research paper.
Image: Archival ALMA view of the asymmetric dust concentration around Oph-IRS 48, released in 2013. This is not an image from the new chemical comparison. Credit: ALMA (ESO/NAOJ/NRAO)/Nienke van der Marel. Source image, used under CC BY 4.0. Reproduced without image edits.
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