Scientists have been puzzled by the quietness of the largest galaxies. Computer models predicted they should be full of new stars, but they contain much less stellar material than expected. Something powerful seems to be stopping star production. The main suspect is the supermassive black holes at the center of these galaxies. When these black holes consume material, they create strong winds. These winds blow through the galaxy, removing the gas and dust needed to form new stars. Until recently, it was hard to see these winds clearly.
The XRISM mission, launched in 2023 by the Japan Aerospace Exploration Agency, NASA, and the European Space Agency, has changed this. Its advanced instruments provide a much clearer view of extreme cosmic environments. Xin "Cindy" Xiang, a researcher at the University of Michigan, used XRISM to study the galaxy NGC 4151, which is about 50 million light-years away. This galaxy has an active nucleus powered by a black hole.
Xiang discovered that winds from the black hole blow at different speeds: slow, fast, and ultra-fast. The fastest winds can even push material out of the galaxy. The most exciting discovery was that these fast winds do not blow all the time. They erupt about 2.8 hours after the black hole releases a burst of X-rays. This timing is the first observational link between X-ray activity and the start of these winds. Xiang developed a new tool called "cindicity" to predict when these fast winds will occur, acting like a cosmic weather forecast.