FAST Unravels the Mystery of Fast Radio Bursts. Image courtesy of the research team.
The chief scientist of China's National Astronomical Observatory, Li Di, and his team at the Five-hundred-meter Aperture Spherical radio Telescope (FAST) have proposed a novel method to comprehensively analyze the behavior of active fast radio bursts in the time-energy phase space. The related research findings were published on April 12th in the form of a cover article in Science Bulletin.
"This discovery reveals the burst patterns of fast radio bursts and demonstrates their emission rules different from other physical phenomena, marking a leap forward in our understanding of fast radio bursts," said Li Di, the corresponding author of the paper, to China Science Daily.
As the most intense cosmic outbursts in the radio band, fast radio bursts release enough energy within a thousandth of a second to power human society for trillions of years. The burst signals, like bright cosmic fireworks, can traverse half the universe and be captured by humans.
The discovery and study of fast radio bursts provide an excellent experimental field for exploring extreme cosmic environments and validating physical theories. In many past studies, all efforts to search for fast radio bursts on millisecond to second timescales have ended in failure. This has led researchers to reconsider the emission modes of fast radio bursts. Periodic searches focus on the occurrence time of burst event sequences, ignoring their energy, especially the possible correlation between the two fundamental physical parameters of time and energy.
In response to thousands of fast radio burst detections by FAST, Zhang Yongkun, a member of Li Di's team, developed a novel "Pincus-Lyapunov phase diagram" analysis method to provide standards for measuring and comparing the randomness and chaos of different celestial events, such as fast radio bursts, pulsars, earthquakes, and solar flares, in the two-dimensional space of time and energy.
Chaos and random events are both unpredictable, but their manifestations differ. The unpredictability of a random sequence is stable over time, such as rolling dice, where no matter how many times you roll, you cannot predict the next roll based on the current outcome. In a chaotic system, unpredictability grows exponentially over time. For example, in the weather system, we can roughly estimate the weather shortly based on the current weather conditions, but it is difficult to accurately predict the weather for the next week. The longer the interval, the more difficult the prediction.
In the phase space of randomness-chaos, fast radio bursts exhibit clear randomness, resembling random walks in spacetime, while earthquakes, solar flares, and other phenomena exhibit significant chaos. The probability of earthquake occurrence depends on the intensity of the earthquake. Large earthquakes are often followed by frequent aftershocks, whereas fast radio bursts do not exhibit such dependency patterns, challenging the model of triggering fast radio bursts by popular theories of dense stellar shell vibrations.
The depth and originality of this study have opened up new directions for exploring the origin theories of fast radio bursts. The high randomness of fast radio bursts suggests that they may originate from multiple interacting mechanisms, and the interactions between these mechanisms will be the focus of the next stage of research. With technological advancements, FAST enables scientists to more accurately capture these dazzling "fireworks" in the universe and explore the secrets they hold.
Related Paper Information:
https://doi.org/10.1016/j.scib.2024.02.010
China Science Daily (2024-04-12 1st Edition, Front Page)
