Black holes – mysterious objects that never cease to fascinate scientists and astronomers – have once again revealed their secrets. A groundbreaking study has shed light on previously unknown features of black holes, in particular microquasars.
Microquasars, which are a special group of stellar-mass black holes, have the ability to launch jets of strongly magnetized plasma. These jets, similar to quasars, are compact regions formed when supermassive black holes cluster in the cores of galaxies. The mass of these black holes exceeds the mass of our Sun by millions and billions of times.
A recent study published in Nature led by UNLV astrophysicist Bing Zhang examines the GRS 1915+105 microquasar system. The team of international scientists used China’s Five Hundred Aperture Spherical Radio Telescope (FAST) to make the groundbreaking observations.
For the first time, the researchers detected a quasi-periodic oscillation (QPO) signal in the radio band from a system of microquasars. QPOs are an essential tool to help astronomers understand the workings of stellar systems, including black holes. While QPOs have previously been observed in the X-ray emission of microquasars, this is the first time they have been detected in the radio emission of the system.
The distinct QPO signal has an approximate period of 0.2 seconds or a frequency of about 5 Hertz. It appears under unique physical conditions and has been detected twice so far, in January 2021 and June 2022. Wei Wang, a professor at Wuhan University and lead researcher of the study, explains that this signal could be evidence of a jet launched by a galactic black hole with stellar mass.
According to Zhang, director of the Nevada Center for Astrophysics and one of the lead authors of the study, X-ray emission in black hole systems usually explores the accretion disk surrounding the black hole. On the other hand, radio emission studies the jet flying out of the disk and the black hole itself. Zhang suggests that the observed QPO signal may be caused by the precession of the jet, which causes its direction to change every 0.2 seconds.
This precession could be caused by a misalignment between the black hole’s rotational axis and its accretion disk. However, Zhang recognizes that there are other possibilities, and further observations will provide more insight into these mysterious QPO signals.
The detection of QPOs in the radio emission of microquasars opens up new possibilities for understanding the behavior and dynamics of black holes. With each new discovery, scientists are getting closer to unraveling the mysteries of these cosmic formations and expanding our knowledge of the Universe.
