Astronomers using the NASA/ESA/CSA James Webb Space Telescope have discovered that dust and water can form and survive surprisingly close to the supermassive black hole at the centre of the Milky Way, according to a new study by an international research team.
The observations focused on IRS 3, a highly evolved star located just 0.55 light-years from Sagittarius A*, the galaxy's central supermassive black hole. The findings reveal that IRS 3 continues to enrich its surroundings with newly formed material despite the intense radiation environment near the black hole.
IRS 3 is in a late stage of stellar life known as the asymptotic giant branch phase, during which stars become huge, cool and luminous, shedding gas into space through powerful stellar winds. This cast-off material is one of the most important sources of cosmic dust, but it had previously been unclear whether such processes could occur so close to a supermassive black hole.
Using Webb's Mid-Infrared Instrument (MIRI), the research team analysed the star's infrared light and identified clear signatures of oxygen-rich dust. For the first time, they also detected water in the star's surrounding envelope.
“Galactic centres are among the most extreme environments, so understanding whether stars can continue enriching their surroundings there is an important question,” said lead author Florian Peißker of the University of Cologne in Germany. “With Webb, we can directly observe how stars behave under these conditions and see that dust production remains remarkably resilient.”
IRS 3 is one of the brightest mid-infrared sources in the galactic centre and has long been notable for its enormous dusty envelope. Previous studies had suggested the star could be carbon-rich, but the new observations point to a different composition. The Webb data revealed two strong infrared signatures associated with silicate dust, made up of silicon and oxygen, identifying IRS 3 as an oxygen-rich evolved star nearing the end of its life and shedding material into space.
“This discovery was possible because of Webb's highly capable infrared instruments,” said Macarena Garcia Marin of ESA, a co-author of the study and principal investigator of the MICONIC programme. “This is the first time a continuous mid-infrared spectrum has been collected for this star, allowing us to detect the features from the silicate dust and uncover the star's true chemical identity.”
By combining Webb's spectral observations with simulations of how light would travel through different models of the star's surrounding envelope, the researchers reconstructed the structure of the material around IRS 3. Their results indicate a layered, shell-like distribution of dust extending roughly 10,000 astronomical units from the star, with temperatures decreasing from approximately 1,200 Kelvin close to the star to around 100 Kelvin in the outer regions.
The observations also provided evidence of water within the envelope of IRS 3, marking the first clear detection of its kind for this object.
“The detection of water is especially exciting because it shows that molecular material can survive in an environment dominated by intense radiation,” Garcia Marin said. “This tells us that even close to a supermassive black hole, stars can continue contributing material back into their surroundings.”
From the observations and accompanying stellar modelling, the researchers estimate that IRS 3 has a mass of approximately six times that of the Sun and is around 72 million years old. The star appears to be undergoing intense mass loss, ejecting material into space and creating the extended envelope observed by Webb.
The findings suggest that evolved stars may continue to play an important role in supplying dust to galactic centres, regions previously thought to be especially hostile to such processes.
The observations were obtained in 2025 as part of the Mid-Infrared Characterisation of Nearby Iconic galaxy Centres (MICONIC) Guaranteed Time Observations programme, using Webb's MIRI instrument.
