The James Webb Space Telescope (JWST) has identified water molecules and oxygen-rich silicate dust in the circumstellar envelope of IRS 3, a dying star located approximately 0.55 light-years from Sagittarius A*, the supermassive black hole at the center of the Milky Way. This discovery, made using JWST’s Mid-Infrared Instrument (MIRI), challenges previous assumptions about the survival of complex molecules in the extreme radiation environment of the galactic center. The findings were published in Live Science, detailing the first confirmed detection of water in such proximity to a supermassive black hole.
James Webb Detects Water and Silicate Dust in Unlikely Galactic Center Environment
Projected Distance and Spectral Analysis Reveal Star’s Chemistry
IRS 3, the brightest L-band source in the Milky Way’s inner parsec, is situated 4.4 arcseconds from Sagittarius A* on the sky. At the galactic center’s distance, this angular separation translates to a projected distance of 0.17 parsecs (about 0.55 light-years). However, the true three-dimensional distance could be greater, depending on the star’s position relative to the black hole. Spectral analysis of mid-infrared light from IRS 3 revealed a strong match between the observed absorption features and water molecules, with the most significant signal detected between 6.0 and 6.25 micrometres. Silicate dust, identified through two distinct absorption bands, further confirmed the star’s oxygen-rich chemistry, overturning earlier classifications that suggested a carbon-rich composition.
Star’s Characteristics and Stellar Winds
IRS 3, a massive asymptotic giant branch star, has a mass approximately six times that of the Sun and an age of around 72 million years. Despite its relatively young age compared to the Sun’s 10-billion-year lifespan, the star emits 60,000 times the Sun’s luminosity. It expels material through violent stellar winds, losing the equivalent of Earth’s mass every 18 days. This ejected matter forms a layered, shell-like envelope extending up to 10,000 astronomical units (about 10,000 times the Earth-Sun distance) from the star. The envelope’s outer regions cool to about 100 kelvins, allowing silicate dust and water vapor to condense. The study, led by Florian Peißker of the University of Cologne, highlights that such stars can still enrich their surroundings with dust and molecular material despite the hostile conditions near Sagittarius A*.
Implications for Galactic Chemistry and Stellar Evolution
Unanswered Questions and Future Research
While the study confirms IRS 3’s ability to produce dust and water near Sagittarius A*, several questions remain. Why does IRS 3 have such a prominent envelope when similar stars are rare in this region? The researchers suggest factors such as the surrounding medium’s influence or unknown interactions may contribute. Future observations with JWST will monitor the envelope’s evolution under the unique conditions of the galactic center. The study, published in Techno-Science, underscores the telescope’s capability to reveal the hidden chemistry of extreme cosmic environments.
