JWST study finds metal-rich gas around Milky Way’s central black hole

Gas orbiting Sagittarius A*, the supermassive black hole at the center of the Milky Way, is rich in elements heavier than helium and hydrogen, according to a peer-reviewed study led by researchers at McGill University’s Trottier Space Institute. The researchers said the enrichment probably resulted from stars that exploded and released material into the black hole’s surroundings over time. The gas also has a composition similar to that of many stars orbiting Sagittarius A*, suggesting that the gas and stars may have formed together. These findings come from imaging analysis of observations made with the James Webb Space Telescope (JWST).

Lead author Nicole Ford, a PhD student in Professor Daryl Haggard’s research group in McGill’s Department of Physics, said the study examined the properties of material available to the black hole, including gas, dust and orbiting stars. “We know there’s a black hole at the centre 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. In astronomy, “metals” includes any element heavier than hydrogen and helium, such as carbon, oxygen, iron or gold. The presence of metals influences how quickly gas cools, which in turn affects how readily the gas can be drawn into a black hole.

The team used JWST infrared observations to distinguish the heat signatures of multiple gas clouds orbiting near Sagittarius A* and to measure the metal composition of each cloud. The analysis investigated the ionization structure and metal enrichment of the Galactic Center minispiral. A companion study led by McGill Banting Postdoctoral Fellow Mayura Balakrishnan tested whether the surrounding gas could preserve evidence of previous bursts of energy from the black hole. The companion analysis found that the gas emission is shaped by local conditions, making it difficult to isolate the black hole’s influence. Rather than ruling out past outbursts, the result indicates that the gas cannot provide a reliable history of Sagittarius A*’s activity.

Ford said that understanding how the black hole attracts material will require comparing the observations with simulations of how gas evolves over longer timescales. The new results may help researchers understand how metals are distributed around supermassive black holes in more distant galaxies, as well as the processes that supplied Earth with many elements. Sagittarius A* is closer to Earth, and therefore easier to see, than any other supermassive black hole, providing a nearby setting in which the composition of gas around a galactic center can be studied in detail. However, the findings do not directly explain the black hole’s comparatively slow consumption of material, and the companion study shows that this gas cannot serve as a dependable record of past black-hole bursts. The two papers were published in The Astronomical Journal and The Astrophysical Journal.

Subject of Research: JWST observations of metal enrichment and ionization in gas orbiting the Milky Way’s central black hole

Article Title: The gas around Milky Way's central black hole is rich in metals, study finds

Article References: The gas around Milky Way's central black hole is rich in metals, study finds. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: Sagittarius A*, Milky Way, James Webb Space Telescope, galactic center, metal enrichment, infrared observations, stellar explosions, black-hole activity, around, Milky, Way's, central