The research primarily relied on observations made by the Smart Eye satellite.
Utilizing Data from Huiyan: China’s First Space X-ray Astronomical Satellite
The study used data from my country’s first space X-ray astronomical satellite, Huiyan. They combined this data with observations from ground-based radio and optical telescopes to find evidence of the formation process of magnetically trapped accretion disks around black holes. The research was done by several universities and observatories in China and institutions in France and Poland.
Understanding Accretion and Black Hole Existence
The physical process by which a black hole captures gas is called “accretion.” This gas falling toward the black hole is called an accretion flow and is in a plasma state. The viscous process in the accretion flow releases gravitational potential energy as radiation in different wavelengths that telescopes can observe. Therefore, by accreting gas, black holes indirectly manifest their existence. Observation of this radiation has become an important way to study black holes.
Unveiling Black Holes: The Role of Magnetic Fields
In 2019, the “Event Horizon Telescope” (EHT) collaboration released the first black hole photo (M87) in human history, unveiling the mystery of the black hole and its surrounding environment that we can “see”. However, an “invisible” magnetic field is also around the black hole.
The Formation of Magnetic-Trapped Disks
As the black hole accretes gas, it drags the magnetic field inward. The theory suggests that as the gas gathers, it brings a weak external magnetic field. As a result, the magnetic field in the inner region of the gas flow will gradually grow. The magnetic field’s effect on the accretion flow will increase over time and eventually balance with the black hole’s gravitational pull. At this time, the matter that has accumulated is trapped by the magnetic field and cannot easily and rapidly enter the horizon of the black hole. This creates a disk that is imprisoned by the magnetic field.
Challenges in Confirming Magnetic-Trapped Disks
The theoretical model of magnetic trapped disks has been very mature and has successfully explained many complex observational phenomena of black hole accretion systems. There is currently no direct proof of magnetic trapped disks. The formation of these disks remains a mystery. Multiple studies have pointed out that there may be a magnetic-trapped disk around the supermassive black hole at the centre of the M87 galaxy. Even with the EHT’s high-resolution observation of M87 and its collection of magnetic field information, including the position type, near the black hole, it cannot confirm the presence of a magnetic trapped disk.
Stellar Black Holes and Unique Observations
In addition to the supermassive black holes at the centres of galaxies, there are stellar black holes in the universe. Nowadays, astronomers have found black holes in several binary star systems.
Revealing the Formation of Magnetic Trapping Disks
The research team studied the black hole X-ray binary star MAXIJ1820+070. They observed a unique delay phenomenon: the jet’s radio radiation and the outer region’s optical radiation lagged behind the accretion. Hard X-rays of hot gas in the inner zone of the accretion (thermal accretion flow) at about 8 and 17 days.
Direct Observational Evidence for Magnetic Trapped Disks
This work shows how the magnetic field is transported in the accretion flow and how a magnetic trapping disk is formed in the thermal accretion flow near the black hole. Therefore, it has become the most direct observational evidence for the existence of magnetically trapped disks so far.
Implications for Scientific Understanding
This research will help us understand important scientific topics like how large-scale magnetic fields are formed in black hole accretion disks of different sizes and how jets are accelerated. This understanding is possible because physical processes apply universally.
Black Hole Accretion Process and Radiant Effects
The research team found that an increase in hard X-ray radiation destabilises more accretion matter in the outer region when a black hole gets closer to finishing the accretion process. This was observed through numerical simulation of the black hole X-ray binary explosion process. The black hole speeds up, creating a bright light outside the swirling matter. This bright light appears 17 days later than the brightest X-ray light emitted by the matter.
