X-Ray Spectra Provide the Sharpest Image Yet of a Rapidly Spinning Black Hole
The universe is full of extreme objects, but few are as fascinating—or as difficult to study—as black holes. In early 2026, astronomers announced a major breakthrough: the sharpest X-ray spectrum ever obtained of a rapidly spinning supermassive black hole. This achievement was made possible by the X-Ray Imaging and Spectroscopy Mission (XRISM), a joint effort between NASA and the Japanese Aerospace Exploration Agency (JAXA), which launched on September 7, 2023.
By combining XRISM’s cutting-edge capabilities with observations from ESA’s XMM-Newton and NASA’s NuSTAR, researchers have taken an unprecedented look at the immediate surroundings of a black hole at the center of the galaxy MCG–6-30-15. The results not only confirm long-standing theories about black hole spin but also reveal new details about how these cosmic giants interact with their host galaxies.
A Galaxy Known for Its Mysterious X-Ray Signals
MCG–6-30-15 is a Type 1 Seyfert galaxy located about 120.7 million light-years from Earth. For decades, astronomers have been intrigued by this galaxy because of its highly variable X-ray emission, which hinted that extreme physical processes were taking place close to its core.
At the center of MCG–6-30-15 lies a supermassive black hole with a mass of roughly two million times that of the Sun. While this might sound enormous, it is actually on the smaller end of the supermassive black hole scale. What makes it special is not just its mass, but how fast it appears to be spinning.
Spin is one of the most fundamental properties of a black hole, along with mass. However, measuring spin is notoriously difficult because it requires observing material orbiting extremely close to the event horizon, where gravity distorts space and time itself.
Why XRISM Changed the Game
Previous X-ray telescopes provided strong hints that much of the X-ray light from MCG–6-30-15 originated near its black hole. The problem was resolution. Older instruments could not clearly separate emission lines from the accretion disk and absorption lines from intervening gas and winds along our line of sight.
XRISM was specifically designed to solve this problem. Its Resolve instrument, an advanced X-ray spectrometer, offers unmatched spectral resolution, allowing astronomers to distinguish subtle features in X-ray light that were previously blended together.
By combining XRISM’s high-resolution data with the broad energy coverage of XMM-Newton and NuSTAR, the research team finally had the tools needed to isolate where different X-ray signals were coming from.
The Signature of a Rapidly Spinning Black Hole
One of the most important findings from this study is the clear detection of a broad, warped iron emission line in the X-ray spectrum. This feature is produced when X-rays emitted by the black hole’s corona reflect off iron atoms in the accretion disk.
Near a black hole, these iron lines become distorted by relativistic effects. The gas in the inner disk is moving at speeds close to the speed of light, and the intense gravity causes gravitational redshift and Doppler broadening. The shape of this line acts as a direct probe of how close the disk extends toward the event horizon—and therefore how fast the black hole is spinning.
The XRISM data confirm that the iron emission originates from matter orbiting extremely close to the black hole, rather than from distant gas clouds or outflowing material. This region produces around 50 times more X-ray reflection than gas located farther away, leaving little doubt that astronomers are seeing the immediate environment of the black hole itself.
Separating Disk Emission from Cosmic Winds
Another major achievement of this study was the ability to disentangle disk reflection from absorption caused by winds flowing away from the black hole.
The data reveal at least five distinct wind zones, each with different physical properties. These winds are driven by accretion—the process by which the black hole pulls in surrounding matter—and they play an important role in regulating how black holes and galaxies evolve.
Before XRISM, it was difficult to determine whether features in the X-ray spectrum were caused by relativistic effects near the event horizon or by winds located much farther out. The new observations clearly show that both are present, but they can now be studied separately and accurately.
A New Look at the Black Hole Corona
The study also provides valuable insights into the corona, a mysterious region of extremely hot plasma that sits above and below the accretion disk. The corona reaches temperatures of billions of degrees and is responsible for producing most of a black hole’s X-ray emission.
Despite decades of study, the corona remains poorly understood. XRISM’s precise spectral measurements help constrain its properties, offering clues about its size, structure, and how it interacts with the disk below. These details are essential for building accurate physical models of black hole systems.
Why Spin and Winds Matter for Galaxy Evolution
Understanding both black hole spin and accretion-driven winds is critical for understanding how galaxies grow and change over cosmic time.
Spin influences how efficiently a black hole converts infalling matter into energy, and it may play a role in launching powerful jets. Winds, on the other hand, can heat or expel gas from a galaxy, potentially slowing or shutting down star formation.
By accurately measuring these properties in systems like MCG–6-30-15, astronomers gain a more complete picture of the symbiotic relationship between supermassive black holes and their host galaxies.
Confirming and Refining Past Measurements
One of the broader goals of this research is to revisit earlier black hole spin measurements that were made using lower-resolution data. XRISM provides a way to test how accurate those earlier estimates were and to refine them where necessary.
This study serves as a proof of concept. If XRISM can deliver this level of detail for MCG–6-30-15, it can do the same for many other active galaxies. Over time, this will lead to a much clearer understanding of how common rapid black hole spin really is across the universe.
Looking Ahead
XRISM is still early in its mission, and these results highlight just how transformative high-resolution X-ray spectroscopy can be. By peeling apart the complex X-ray signals from extreme environments, astronomers are now able to directly test predictions of Einstein’s theory of General Relativity in some of the most intense gravitational fields known.
As more observations roll in, XRISM is expected to play a central role in black hole physics, neutron star research, and studies of hot cosmic plasma throughout the universe.
Research paper:
Brenneman, L. W. et al., A Sharper View of the X-Ray Spectrum of MCG–6-30-15 with XRISM, XMM-Newton, and NuSTAR, The Astrophysical Journal (2025).
https://doi.org/10.3847/1538-4357/ae1225
