The Japan-led XRISM (X-ray Imaging and Spectroscopy Mission), in collaboration with NASA and ESA, has made a remarkable discovery by identifying iron fingerprints in the nearby active galaxy NGC 4151. The mission’s Resolve instrument captured a detailed spectrum of the area around the galaxy’s central supermassive black hole, revealing the presence of various elements and providing insights into the fate of matter near the black hole.
NGC 4151: A Cosmic Laboratory for Black Hole Studies
NGC 4151, a spiral galaxy located approximately 43 million light-years away in the constellation Canes Venatici, is one of the closest-known active galaxies. Its central supermassive black hole, with a mass more than 20 million times that of the Sun, is surrounded by a bright and variable accretion disk, twin jets of particles, and a puffy donut-shaped torus. The galaxy’s proximity and unusually bright X-ray emissions make it an ideal target for studying the interaction between black holes and their surroundings.
Iron Fingerprints Revealed by XRISM’s Resolve Instrument
XRISM’s Resolve instrument detected a sharp peak at energies just under 6.5 keV (kiloelectron volts) in NGC 4151’s spectrum, indicating the presence of an iron emission line. Astronomers believe that much of the power in active galaxies originates from X-rays produced in hot, flaring regions close to the black hole. When these X-rays bounce off cooler gas in the accretion disk, they cause iron to fluoresce, resulting in a specific X-ray peak. This discovery helps astronomers better understand the structure and dynamics of the accretion disk and the erupting regions near the black hole.
“XRISM’s Resolve instrument captured a detailed spectrum of the area around the black hole,” said Brian Williams, NASA’s project scientist for the mission at the agency’s Goddard Space Flight Center in Greenbelt, Maryland. “The peaks and dips are like chemical fingerprints that can tell us what elements are present and reveal clues about the fate of matter as it nears the black hole.”
The spectrum also exhibited several dips around 7 keV, caused by iron absorption in the cooler torus material surrounding the accretion disk. XRISM’s ability to detect various elements, such as sulfur, calcium, and argon, in addition to iron, provides astrophysicists with valuable information about the cosmic phenomena scattered across the X-ray sky.
