Surprising Discovery at the Heart of Our Galaxy

An international team of astronomers, utilizing the James Webb Space Telescope (JWST) from NASA, ESA, and CSA, has made a remarkable discovery regarding the presence of dust and water in close proximity to the supermassive black hole at the center of our Milky Way. Observations reveal that the advanced star IRS 3 continues to enrich its surroundings with newly formed material, despite the intense radiation environment near Sagittarius A*.

These new observations provide the most detailed representation of the evolved star IRS 3 in the mid-infrared spectrum to date. Located a mere 0.55 light-years from Sagittarius A*, IRS 3 is nearing the end of its life cycle, specifically in the asymptotic giant branch phase. Stars in this phase are characterized by their large size, cool temperatures, and bright luminosity, emitting powerful stellar winds that eject gas into space. This expelled stellar material is a crucial source of cosmic dust, yet it was previously uncertain whether a star could produce such material while being so close to a supermassive black hole.

The research team, through the analysis of infrared light from the star using the Mid-Infrared Instrument (MIRI) of the Webb Telescope, identified definitive signatures of oxygen-rich dust and detected water in the star's envelope for the first time. The findings indicate that even under the extreme conditions near a supermassive black hole, evolved stars like IRS 3 can still produce dust and other materials essential for the formation of future generations of stars and planets.

"Galactic centers are among the most extreme environments, so it is a significant question whether stars can continue to enrich their surroundings with dust there," stated lead author Florian Peißker from the University of Cologne. "With the Webb Telescope, we can directly observe how stars behave under these conditions and see that dust production remains remarkably stable."

IRS 3 stands out as one of the brightest infrared sources in the galactic center and has long been noted for its extensive dust envelope. Previous studies suggested a high carbon content in the star, but the latest observations paint a different picture. Data from the Webb Telescope revealed two strong infrared signatures associated with silicate dust, a combination of silicon and oxygen. These characteristics identify IRS 3 as an oxygen-rich, evolved star that is shedding material into space.

"This discovery was made possible thanks to Webb's high-performance infrared instruments," remarked Macarena Garcia Marin from ESA, a co-author of the study and project leader of the MICONIC program. "This is the first time a continuous spectrum in the mid-infrared range has been captured for this star, allowing us to identify the features of silicate dust and uncover the true chemical identity of the star."

By combining Webb's observations of the star's spectrum with simulations of the emitted light's propagation through various models of the surrounding envelope, the team reconstructed the structure of the star's envelope. Their results suggest a layered, shell-like distribution of dust extending approximately 10,000 astronomical units from the star. Temperatures in this region range from about 1,200 Kelvin near the star to around 100 Kelvin in the outer areas. The observations also provided evidence of water within the IRS 3 envelope — the first definitive detection of this kind for this object.

"The detection of water is particularly exciting because it shows that molecular material can survive in an environment with intense radiation," said Garcia Marin. "This means that stars can continue to release material into their surroundings even near a supermassive black hole."

Based on observations and stellar modeling, researchers estimate that IRS 3 has about six times the mass of the Sun and is approximately 72 million years old. The star appears to be experiencing significant mass loss, propelling material into space and forming the extensive envelope observed by Webb. These findings suggest that evolved stars may continue to play a crucial role in supplying dust to galactic centers — regions previously thought to be particularly hostile to such processes.

The observations were conducted in 2025 as part of the "Mid-Infrared Characterization of Nearby Iconic Galaxy Centers (MICONIC) Guaranteed Time Observations" (#1266) using the MIRI instrument of the Webb Telescope.

These results were published in the journal Astronomy and Astrophysics.

Background Information

The Webb Telescope is the largest and most powerful telescope ever launched into space. Under an international cooperation agreement, ESA provided the launch service for the telescope using the Ariane 5 rocket. In collaboration with its partners, ESA was responsible for the development and qualification of the Ariane 5 adaptations for the Webb mission, as well as securing the launch service through Arianespace. Additionally, ESA provided the main spectrograph NIRSpec and 50% of the Mid-Infrared Instrument MIRI, developed and built by a consortium of publicly funded European institutions (the MIRI European Consortium) in collaboration with JPL and the University of Arizona.

Webb is an international partnership between NASA, ESA, and the Canadian Space Agency (CSA).