The black hole at the center of our galaxy is not surrounded by clean, untouched gas. Using the James Webb Space Telescope, astronomers have found that the material orbiting Sagittarius A* is rich in heavy elements — the chemical leftovers of stars that lived and died near the heart of the Milky Way.
The study, led by McGill University PhD student Nicole Ford and published in The Astronomical Journal, measured metal abundances of about 1.8 times the Sun’s level in parts of the Galactic Center Minispiral, a structure of warm ionized gas and dust within the innermost 0.1 parsec around the black hole.
What Webb saw at the center of the Milky Way
Ford’s team used Webb’s Mid-Infrared Instrument and its Medium Resolution Spectrograph to separate the heat signatures of individual gas clouds close to Sagittarius A*. That detail allowed the researchers to measure the composition of distinct features in the Minispiral, including the Bar, the Northern Arm and fast-moving compact structures moving toward us.
Sagittarius A* contains roughly four million times the mass of the Sun and is the nearest supermassive black hole to Earth. Its closeness gives astronomers their best chance to inspect the fuel supply around a quiet giant of this scale.
Why astronomers call it “metal-rich”
In astronomy, “metals” does not only mean substances such as iron or gold. It means every element heavier than hydrogen and helium, including carbon, oxygen and sulfur. Those elements are created inside stars and spread into space when massive stars explode as supernovae.
The researchers found that the gas has a composition similar to many of the stars orbiting the black hole. That resemblance suggests the gas and stars may have formed together, rather than the gas arriving later from somewhere else in the galaxy.
A clue left by dead stars
The enrichment probably built up over time as generations of stars exploded and released material into the black hole’s surroundings. A supernova remnant called Sgr A East overlaps the region on the sky, and related research indicates that it injected heat into the gas and helped keep the environment turbulent for roughly 10,000 years.
That chemistry matters because metals change how gas behaves. Metal-rich gas can cool more efficiently, and cooling helps gas compress and fall inward. Yet Sagittarius A* still consumes only a slow trickle compared with many other supermassive black holes.
Why the black hole still eats so slowly
“We know there’s a black hole at the center of our galaxy pulling material into itself, but we see that it’s eating a lot less material than other supermassive black holes, and more slowly,” Ford said. Understanding that slow feeding means studying the gas, dust and stars available for the black hole to consume.
The new measurements help explain part of that puzzle: the available material is chemically enriched, but an abundance of about 1.8 times solar is still modest, while heat and turbulence in the galactic center work against a smooth flow inward. The next step is to compare Webb’s observations with computer simulations that follow the gas over much longer timescales.
Because Sagittarius A* is so close, what astronomers learn here can guide studies of black holes in distant galaxies that cannot be examined in the same detail. The work also traces part of the cosmic recycling process that eventually supplied planets such as Earth with many of the elements they contain.
Sources: McGill University announcement (October 19, 2026); Ford et al., “Ionization Structure and Metal Enrichment of the Galactic Center Minispiral Observed with JWST,” The Astronomical Journal (2026), DOI: 10.3847/1538-3881/ae994d; Universe Today.