When researchers first captured the groundbreaking image of a black hole in 2019, it was a momentous occasion in the field of astrophysics. However, this monumental feat was just the beginning. Recently, scientists have delved even deeper into the secrets of the supermassive black hole situated at the core of the galaxy Messier 87 (M87). Through a meticulous analysis of 22 years’ worth of observations, these astrophysicists have now confirmed that the black hole in M87 is indeed spinning. This revelation adds another layer of intrigue to our understanding of these enigmatic cosmic entities.
To study the black hole in M87, an international team of researchers utilized a global network of over 20 telescopes. By analyzing 170 observations taken between 2000 and 2022, they made some fascinating discoveries. While the black hole’s gravitational pull prevents direct observations of its interior, researchers were able to track its powerful jet extending across a staggering distance of 4,900 light years. This jet, which appears to move at nearly five times the speed of light due to a phenomenon known as superluminal motion, has captivated scientists for over a century. Their current understanding suggests that radiation and particles are channeled along the magnetic field lines of the black hole, resulting in the formation of these extraordinary jets.
A Subtle Dance
In their analysis, the researchers observed intriguing changes in the angle of M87’s jet. Over an 11-year period, the black hole slowly shifted the orientation of its jet by approximately 10 degrees before returning to its original position. This cycle of variation provided a crucial clue in determining the presence of a spinning black hole. As black holes rotate, they induce a phenomenon known as frame-dragging, whereby space-time itself is twisted around them. This gravitational effect causes both the accretion disk and the jet to tilt. By meticulously studying the subtle changes in M87’s jet, the researchers were able to infer the rotational motion of the black hole at its core.
M87 holds a unique position of interest in the scientific community. Situated a mere 54 million light-years away, it is relatively close compared to other galaxies. Furthermore, its celestial beauty has fascinated astronomers for centuries. In 1781, Charles Messier first observed this galaxy while gazing through his telescope in the constellation Virgo. Since then, this celestial wonder has been officially named Messier 87 (M87) in his honor.
The speed at which black holes rotate has long been a topic of intrigue for scientists. Most black holes are believed to spin at velocities close to that of light itself. In fact, previous studies have already demonstrated the remarkable rotational speeds of specific black holes. For instance, in 2013, a black hole situated at the center of the NGC 1365 galaxy, approximately 60 million light-years away, was found to rotate at an astonishing 84 percent of the speed of light. Moreover, in 2019, scientists utilized patterns in X-ray pulses to infer that another black hole was spinning at 50 percent of the speed of light. But what mechanisms are at play that allow these cosmic entities to rotate so rapidly?
When matter collapses into a black hole, it undergoes an immense compression, resulting in an extremely dense singularity. Surprisingly, despite this intense compression, the matter retains its angular momentum. This phenomenon can be likened to an ice-skater who spins faster as they pull their arms inward. In a similar fashion, when matter originating from a rotating star collapses into a black hole, the rotational speed increases due to the conservation of angular momentum.
The recent confirmation of the spinning black hole at the center of M87 marks yet another remarkable milestone in our quest to unravel the mysteries of the universe. Through the painstaking analysis of decades worth of observations, astrophysicists have provided an invaluable glimpse into the intricate mechanisms that govern these cosmic entities. As our understanding of black holes continues to deepen, we inch closer to solving the enigma they represent and grasp the profound implications they hold for our understanding of the cosmos.