Login
Water Found in Stellar Envelope Near the Milky Way’s Central Black Hole
Astronomers using NASA’s James Webb Space Telescope have discovered water molecules inside the enormous envelope of gas and dust surrounding IRS 3, an aging star located remarkably close to the supermassive black hole at the centre of the Milky Way. The finding challenges the long-held assumption that the intense radiation and gravitational turbulence around Sagittarius A, commonly known as Sgr A, would prevent molecules from surviving in such a hostile environment.
IRS 3 lies about 0.6 light-years from Sgr A*, a distance equivalent to roughly 42,000 times the separation between Earth and the Sun. In everyday terms, that is an immense distance. On the scale of the Galactic Centre, however, it places the star in the immediate neighbourhood of a black hole containing approximately four million times the mass of the Sun. The region is crowded with stars, powerful magnetic fields, energetic particles and rapidly changing radiation, making IRS 3 an exceptional natural laboratory for studying how stars evolve under extreme conditions.
The observations were conducted with the Mid-Infrared Instrument, or MIRI, aboard the James Webb Space Telescope. Mid-infrared light is particularly useful for investigating cool dust and molecules that absorb and re-emit radiation at characteristic wavelengths. By analysing the infrared spectrum of IRS 3, researchers led by PD Dr Florian Peißker of the University of Cologne identified the chemical and physical properties of the material surrounding the star with far greater detail than previous observations allowed.
What makes IRS 3 especially striking is the scale of its circumstellar envelope. The structure extends to a radius of approximately 10,000 astronomical units, where one astronomical unit is the average distance between Earth and the Sun. Such envelopes are common around mature, evolved stars, but IRS 3 appears to be unusually isolated in the immediate vicinity of Sgr A*. Its enormous shell of material therefore stands out against a dense background containing millions of other stars.
The new observations indicate that IRS 3 is undergoing a phase known as a superwind. This is a brief but dramatic stage in the late evolution of certain stars, particularly asymptotic giant branch stars. During this phase, powerful stellar winds carry gas and newly formed dust away from the star at extremely high rates. Over periods of only a few centuries, the star can lose a substantial fraction of its outer layers, transforming its surroundings into a thick, expanding envelope that will eventually disperse into interstellar space.
According to the research team, IRS 3 is losing material at a rate equivalent to the mass of Earth every 18 days. Although the comparison makes the scale easier to imagine, the total outflow is far more significant when considered over astronomical timescales. The steady loss of gas and dust explains why the envelope is both unusually large and dense. It also provides the raw material in which molecules can form, shielded within cooler regions of the expanding stellar outflow.
The detection of water is the most surprising aspect of the study. Near Sgr A*, ultraviolet radiation, X-rays and high-energy particles are expected to break apart fragile molecules. Water molecules can be destroyed when energetic photons dissociate them into their constituent atoms, particularly in exposed regions close to powerful sources of radiation. Yet the MIRI observations show that water exists within the envelope of IRS 3, suggesting that the dense outflow from the star creates protected pockets where molecular chemistry can proceed.
This discovery does not mean that the Galactic Centre is a calm or hospitable environment. Instead, it demonstrates that stellar mass loss can temporarily create its own chemical refuge. The material expelled by IRS 3 increases the density of gas and dust around the star, allowing some regions of the envelope to absorb damaging radiation. Within these shielded zones, atoms can combine on dust grains or in the gas phase, producing molecules that would otherwise be rapidly destroyed. The finding offers a new view of how evolved stars may enrich even the most violent regions of a galaxy.
The researchers say that IRS 3 may be actively supplying the area around Sgr A* with elements and molecules that later become part of the broader interstellar medium. Water itself is not evidence of life, but it is a crucial ingredient in planetary formation and a central component of the chemistry that precedes biology. As the envelope expands, some of its contents will eventually mix with surrounding gas, potentially influencing the composition of future stars, planets and smaller bodies formed in the Galactic Centre.
The study, published in Astronomy & Astrophysics, also highlights the scientific value of observing the Milky Way’s centre at infrared wavelengths. Visible light is heavily obscured by dust along the line of sight, while infrared radiation can pass through much of that material and reveal otherwise hidden structures. Future observations with METIS, a next-generation mid-infrared instrument being developed for the Extremely Large Telescope in Chile, could provide sharper views of IRS 3’s envelope, measure its winds in greater detail and determine how its molecular content changes over time. For now, the star’s unexpected water-rich cocoon is offering astronomers a rare glimpse of stellar chemistry unfolding beside one of the most extreme objects in the universe.
Subject of Research: Not applicable
Article Title: Dust production in the harsh environment of Sgr A* – MIRI/JWST observation of the O-rich asymptotic giant branch star IRS 3
News Publication Date: 11-Aug-2026
Web References: https://doi.org/10.1051/0004-6361/202660243
References: Astronomy & Astrophysics
Image Credits: ESO/F. Peissker
Keywords
James Webb Space Telescope, JWST, MIRI, IRS 3, Sagittarius A, Sgr A, Milky Way, Galactic Centre, water molecules, superwind, asymptotic giant branch star, stellar evolution, circumstellar envelope, dust production, black hole, infrared astronomy, Extremely Large Telescope
a 361 euro
