A dozen years ago, astronomers first discovered the X-ray quasi-periodic oscillation signal from a supermassive black hole-"Heartbeat of a black hole". More than ten years later, when the astronomer once again had the opportunity to observe the black hole, he found that the signal was still continuing. The research work was led by the National Astronomical Observatory High Energy Astrophysics Group, and collaborators included the Durham University research team. The relevant results were published in the "Royal Astronomical Society Monthly" on June 10.

  This special black hole is named RE J1034+396, and it is a supermassive black hole 600 million light-years away from the earth with a mass of 2 million suns. In 2007, scientists used the European Space Agency’s XMM-Newton satellite to discover for the first time that the black hole’s X-ray radiation had a periodic oscillation signal of about an hour. After 2011, because the black hole's line of sight was too close to the sun, the monitoring of its heartbeat signal also stopped. Until 2018, scientists once again had the opportunity to observe this black hole. The research team applied to the European Space Agency and NASA for the use of XMM-Newton satellite, "Nuclear Spectroscopic Telescope Array" satellite and "Yuyan" satellite to carry out joint observations on RE J1034+396, and successfully completed all observations in October 2018 task. After detailed data analysis, the team finally confirmed that the X-ray oscillation signal of RE J1034+396 still exists and is stronger than 10 years ago! This is the longest duration of the ultra-massive black hole heartbeat signal observed so far.

  There are a large number of black holes in the universe with a mass of one million to hundreds of millions of suns. The "Kagangtuya" black hole in the movie "Interstellar" is such a big black hole. The material floating in the interstellar space will be captured by the gravity of the black hole. In the process of gradually falling into the black hole, a disc-shaped structure will be formed, and a large amount of energy will be released in the small space around the black hole, resulting in a very large Strong high-energy radiation, such as X-rays. However, such periodic repetitive signals of high-energy radiation are rarely found. The period of this signal carries key information about the scale and structure of matter near the black hole horizon.

  It is understood that the currently known black hole that can generate a heartbeat-like signal is a small black hole called GRS 1915+105 located in the spiral arm of the Milky Way. The mass of the black hole is only 12 solar masses. It is rapidly absorbing material from a star next to it and generating an X-ray heartbeat signal with a "heart rate" of about 67 Hz. Through a simple quality comparison, the scientists estimated the "theoretical heart rate" of RE J1034+396 and found that it was consistent with the "measured heart rate".

  Researcher Jin Chichuan, the first author and corresponding author of the paper, said: "This heartbeat signal is very beautiful! It proves for the first time that such a periodic signal from a supermassive black hole can be stable for a long time, and provides us with an in-depth study of its physical mechanism and origin. Important clues and excellent opportunities. RE J1034+396 can also become one of the important observation targets of China's next-generation X-ray astronomical satellites, such as the Einstein probe and other satellites.

  At present, the research team is conducting an in-depth analysis of the data of multiple satellites with a view to understanding more about the nature of the heartbeat signal and comparing it with the small-mass black holes in the Milky Way to obtain more information on the physical processes near the black hole horizon Deeply understand. (Headquarters CCTV reporter Shuai Junquan)