Water is not only a vital resource for us on Earth, but also one of the most common and mysterious molecules in the universe. It occurred before the formation of the solar system, but its story ends there. Water goes through different cycles of destruction and creation, depending on the conditions in which it is placed. And one of these conditions is the presence of ultraviolet radiation, which can destroy or create water within the disk that makes up the planet. This surprising discovery was made by an international team of astronomers including Else Peters and Jean Kami from the University of Western Ontario. They used the most powerful James Webb Space Telescope (JWST), which launched at the end of 2021. JWST will be able to penetrate the deepest, darkest regions of the universe and study the complex chemical processes that occur there. One of the team’s research targets was d203-506, a protoplanetary disk located at the center of the Orion Nebula, one of the most famous and beautiful formations in the sky. The Orion Nebula is a nursery for planetary systems where new stars and planets are born. But it is also the site of intense ultraviolet radiation emitted by massive stars. It is this radiation that influences the fate of water within disk d203-506. As scientists explain, when ultraviolet light hits a water molecule, it breaks it down into hydrogen and oxygen atoms. The hydrogen atoms fly off into space, but the oxygen atoms remain in the disk. Then, when ultraviolet light hits an oxygen atom, the oxygen atom combines with another oxygen atom to form an oxygen molecule. When UV light hits an oxygen molecule, it can strip the oxygen atom away, leaving behind a hydroxyl molecule. Hydroxyl is an important intermediate in the formation of water because it can combine with hydrogen atoms that come from other sources such as comets and asteroids. In this way, water can again form inside the window glass. This cycle of destruction and water production occurs very intensively in disk d203-506. Scientists estimate that the equivalent of all the water that makes up Earth’s oceans evaporates and reconstitutes within this disk every month. This means that water in the universe is not static and unchanging, but dynamic and adaptive. They can adapt to different conditions and go through different stages of existence. How were scientists able to discover this amazing process? They used the unique ability of the James Webb Telescope to observe the radiation that molecules emit when they interact with ultraviolet light. did. This radiation has specific properties depending on the type of molecule and its state. For example, when a hydroxyl molecule is formed or destroyed, a photon of a specific wavelength and intensity is emitted. These photons can be detected using a spectrometer that is part of the James Webb Telescope. A spectrometer separates light into different colors and measures their intensity. This will allow scientists to determine which molecules are present within the disk and how they change when exposed to ultraviolet light. But to correctly interpret this data, scientists also needed help from experts in quantum physics. Quantum physics studies the behavior of atoms and molecules at the smallest level. This allows us to understand what energy levels molecules have and how they switch between energy levels when absorbing or emitting light. These transitions determine the spectral lines displayed by the spectrometer. The scientists collaborated with colleagues in Spain and the Netherlands and performed complex quantum mechanical calculations to recreate the spectra of hydroxyl and oxygen molecules under different conditions. This helped to compare the theoretical model with the observed data and confirm the hypothesis. This research is part of the PDRs4All Early Science Use Program selected by NASA to demonstrate the capabilities of the James Webb Telescope. PDRs4All is an international consortium of astronomers, physicists, chemists, and mathematicians from different countries. The goal of this program is to study the photodissociation region (PDR), the region of space where ultraviolet light affects the chemistry of materials. PDRs are found in many places in the universe, including near nebulae, planet-forming disks, and black holes. By studying PDRs, scientists can learn more about the origin and evolution of stars, planets, and life. This research is an example of how modern science requires collaboration and integration across disciplines. Astronomy, physics, chemistry and mathematics work together to unlock the secrets of the universe. The James Webb Telescope is a powerful instrument that opens new horizons of scientific discovery. This allows us to see things we couldn’t see before and understand things we couldn’t understand before.

source: Marion Zannese et al, OH as a probe of the warm-water cycle in planet-forming disks, Nature Astronomy (2024). DOI: 10.1038/s41550-024-02203-0