For the first time, a scientific group of specialists from Ural Federal University and colleagues from Moscow and Urumqi (China) have created detailed maps of interstellar ices in the shells of forming stars. To do this, the researchers studied the youngest and most active objects in the Orion A molecular cloud. The data obtained showed how the composition of stars evolves, and will help predict what chemical composition planets forming in such systems may have. The scientists published a description of the results in The Astrophysical Journal. The work was supported by the Russian Ministry of Science and Higher Education (state assignment FEUZ-2025-0003).

"We used data from the James Webb telescope, which has a sensitivity more than 100 times higher than the capabilities of previous telescopes, and about 10 times better angular resolution," says Igor Petrashkevich, an employee of the UrFU Laboratory of Astrochemistry.

The spectra from the telescope were compared with laboratory spectra of space ice analogues obtained at the UrFU ISEAge facility. The comparison helped to identify the chemical composition of the ice with high accuracy, even in extremely difficult cases.

"This allowed us to see for the first time the spatial distribution of ices around young stars and to build pixel-by-pixel absorption maps for key components of space ice, including water, carbon dioxide, carbon monoxide, cyanate ion, ammonium ion and formaldehyde. As a result, the spatial resolution of the maps made it possible to discern the structure of the inner protostellar shells. For us, it's like moving from disparate points on a map to a detailed terrain plan," adds Igor Petrashkevich.

A protostar is a star at an early stage of formation that forms when a gas and dust cloud is compressed by gravity. Thermonuclear reactions are not yet taking place in it, but it is already releasing energy due to gravitational compression. Its shell, a gas and dust cloud, consists of the substance of an interstellar cloud, surrounds the forming protostar and feeds its mass due to accretion.

The scientists studied six Class 0 protostars (HOPS-56, HOPS-60, HOPS-73, HOPS-91, HOPS-96, and HOPS-108) in the Orion A molecular cloud. These are the youngest and most active star-forming objects surrounded by dense dust shells. The analysis of the maps showed that ice is formed mainly at the prestellar stage and evolves together with the protostar, forming the foundation for the chemical composition of planetary systems. At the same time, the composition of the ice turned out to be heterogeneous.

The scientists compared the contents of different molecules in the shells and found that protostars can be divided into two groups based on the relative abundance of ice. This may indicate differences in the evolutionary age of protostars or the conditions in the shells (temperature and density).

"We didn't just make maps – we traced the chemical changes taking place during the evolution of the protostar. For example, a decrease in carbon monoxide content near a central source indicates that the ice is heating up and the molecules are escaping from the dust particles. This is a key mechanism that enriches the gas in an emerging planetary system with complex molecules potentially important for the origin of life. Our work is an important step towards understanding how the "building blocks" of planets are distributed in space. In the future, our results will help refine models of chemical evolution and predict what chemical composition planets forming in such systems may have," explains Anton Vasyunin, head of the UrFU Laboratory of Astrochemistry.

Delfina Zakharova