In a study published in The Astrophysics Journal, a Michigan State University researcher used the NASA Chandra X-Ray Observatory telescope to detect X-rays originating from a black hole.
X-ray data gathered by the Chandra telescope from the center of M31, highlighting the four nuclear sources S1, SSS, N1, and P2. P2 corresponds to the position of the supermassive black hole at the center of the Andromeda galaxy. Image Credit: DiKerby, Zhang, & Irwin 2025, ApJ
Every large galaxy has a supermassive black hole, but the exact nature of the relationship between the two is still mysterious. After analyzing data [from the Chandra telescope], I had a chill, because I realized I was looking at the X-rays from a supermassive black hole flicker on and off.
Stephen DiKerby, Research Associate, Physics and Astronomy College of Natural Science, Michigan State University
Supermassive black holes are objects with millions or billions of times the mass of the Sun, squeezed into such a small space that light cannot escape. Material falling into the black hole's strong gravity might reach an extremely high temperature.
Telescopes, like the Chandra X-ray Observatory orbiting the Earth, can observe X-rays from the environment around supermassive black holes.
DiKerby and his colleagues, who are also members of the IceCube Neutrino Observatory, analyzed 15 years of Chandra data. They then put together a record of the X-ray light emitted by the M31 star, also known as M31*, a supermassive black hole in the Andromeda galaxy.
Their study sheds light on the special bond that exists between a galaxy and its black hole. This is essential to comprehending the evolution of the cosmos throughout the last 14 billion years.
It Began with a Line of Neutrino Breadcrumbs
The story starts with neutrinos, which are little, electrically neutral particles that speed through space to reach Earth. To learn more about the workings of the universe's most extreme systems, DiKerby and his IceCube colleagues track neutrinos through space like a trail of breadcrumbs. The surroundings of supermassive black holes like M31* may produce neutrinos.
DiKerby added, “Chandra has such fine spatial resolution that it can pick apart the X-ray emission from M31* from three other X-ray sources that crowd around it in the core of Andromeda. It is the only telescope that can do this. We were able to reconstruct the image zoom and enhance like in a cop TV show to pick apart the emission to only measure the X-rays from M31*, not the other sources.”
Winking Photons Illuminate the Black Hole
They concluded that since 2006, when it released a spectacular X-ray flare, M31* has been in an elevated state. They also found that before settling into the post-2006 state, M31* had another X-ray flare in 2013.
This result is consistent with a recent IceCube discovery that connected another galaxy's supermassive black hole to neutrino-related flares. These findings demonstrate how temporal windows for neutrino emissions can be inferred from studies of adjacent supermassive black holes.
Their research pinpointed the location of the supermassive black hole to P2 using the exact coordinates of four X-ray sources located deep within the Andromeda galaxy’s core: S1, SSS, N1, and P2.
DiKerby compares monitoring the X-ray brightness of these objects to measuring the intensity of four flickering candles at the far end of a football stadium while standing in one end zone. The researchers were able to isolate each of the nearby objects by differentiating the data using the Chandra telescope’s power and resolution.
The only reason this study is feasible is because of Chandra’s exceptional observing skills. Even though the telescope is still functioning effectively, financing for it could be cut off. The development of AXIS, a potential next-generation telescope, is currently in its early phases and is not expected to be operational until the 2030s.
DiKerby noted, “If Chandra is turned off, the resource to do these fine-resolution observations would go away forever. Maintaining these capabilities and planning for the next generation of telescopes is vital.”
DiKerby expects that this study will encourage others to keep analyzing M31* data. While preparations for future telescope development continue, the Chandra telescope needs to be maintained.
“I want us to keep watching the system, to keep watching these flares, and to continue to write the history of supermassive black holes,” concluded DiKerby.
Journal Reference:
DiKerby, S., et al. (2025) Fifteen Years of M31* X-Ray Variability and Flares. The Astrophysical Journal. doi.org/10.3847/1538-4357/adb1d5.