A recent study confirmed that the BZ-jet model, which attributes black hole jet formation to the extraction of spin energy, accurately describes the observed characteristics of jets from the supermassive black hole in Messier 87, offering substantial evidence of its validity over the competing disk-jet model. Credit: SciTechDaily.com
Black holes are fascinating cosmic entities characterized by gravitational pulls so intense that not even light can escape once it crosses into their event horizons. Yet, intriguingly, more than a hundred years ago, it was discovered that right outside the event horizon, black holes can produce potent streams of matter and energy, referred to as jets, which can travel nearly as fast as light. Telescopic observations have shown these jets extending directly outward in focused streams, resembling laser beams, with some jets reaching lengths that exceed entire galaxies.
Since the discovery of jets, many scholars, including Nobel Laureate Sir Roger Penrose, have studied the formation of these enigmatic phenomena. Currently, two main models attempt to explain jet formation: The “BZ-jet model,” named for the researchers Blandford and Znajek and now the most influential model, posits that a jet is formed by extracting spin energy from a
Evaluating Jet Formation Models
Although the BZ-jet model had already been used by other researchers to simulate general relativistic collimated outflows—effectively, jets—it was unclear whether the BZ-jet model could explain the observed morphology of an actual jet, including its elongated structure, width, and limb-brightening, i.e., its increased brightness near the edge of the jet.
To investigate the validity of these two models, an international team led by Dr. Yuan Feng from the Shanghai Astronomical Observatory of the Chinese Academy of Sciences calculated the jets respectively predicted by these two models for the supermassive black hole at the center of Messier 87 (M87), a giant galaxy in the constellation Virgo. The team then compared its calculations with actual observations of the M87 jet, which had been recorded in the first-ever image of a black hole captured by the Event Horizon Telescope (EHT). The team’s research showed that the BZ-jet model accurately predicted the morphology of the observed M87 jet, while the disk-jet model struggled to explain the observations. The study was published in DOI: 10.1126/sciadv.adn3544