According to a new study published in Nature, the world's top scientific journal , Chinese astronomers have picked up a strong repetitive radio signal from deep in the universe, with 1,863 repeat detections in 54 days, through the Chinese celestial eye FAST. So, who is sending this repetitive signal? Should we reply?
FAST is a giant radio telescope with an aperture of 500 meters, which is the world's largest single-fill aperture radio telescope. Because of its huge aperture, FAST has a very high sensitivity and signal-to-noise ratio and can be used to detect various radio signals in the universe.
We can see objects because light carries information about them to our eyes, and this light is called visible light. And we can use our cell phones to connect to wireless networks for Internet access, because the line electrical signals can carry information to spread, these signals are also essentially light, just invisible to the naked eye.
Radio signals, like visible light, are electromagnetic waves (in addition to microwaves, infrared, ultraviolet, X-rays, gamma rays, etc.), all moving at the speed of light. The difference between electromagnetic waves is that the wavelength or frequency is different, and different wavelengths of light need to be detected with different observation equipment.
The universe is rich in wire-free waves that arrive on Earth invisible to our naked eyes but can be detected by radio telescopes such as FAST. This time the radio signal detected by FAST is special, it is called FRB 20201124A, which is a fast radio burst.
Astronomers first became aware of the existence of fast radio bursts in 2007, and the mechanism of their formation has been deeply troubling astronomers ever since. These radio waves only burst for a few milliseconds, but the energy released is extremely large, equal to the total amount of energy produced by the Sun over a period of days or even a year.
The unusually high dispersion of the fast radio bursts means that their sources are located far beyond the Milky Way. However, fast radio bursts only appear once at random in a region of the sky and then disappear without a trace, so it is very difficult to find their source.
But by chance, astronomers have discovered rare repetitive fast radio bursts, signals that recur many times, a great opportunity to study their origin. FRB 20201124A, the one studied by FAST this time, is exactly a signal with multiple repeated bursts.
Over the course of 54 days, FAST received a total of 1863 repetitive signals from FRB 20201124A, making it one of the most active fast radio bursts observed to date. Based on the observational data, astronomers have located the source of this signal from a distant barred spiral galaxy that is 1.3 billion light-years away from Earth.
The study shows that this is the first fast radio burst to show changes in Faraday rotation measurements, implying the existence of a complex magnetization environment near the source. In another new study published in Nature Communications , our astronomers propose a model to explain the origin of the signal.
Astronomers believe that the duplicate signal came from a binary star system. One is thought to be a magnetar, a neutron star formed by the collapse of a dead star's core, with a magnetic field that is tens of trillions of times stronger than the Earth's surface geomagnetic field. The other is a Be star, which is an extremely hot and rapidly rotating star.
The propagation of radio waves through the disk around the Be star when this magnetar orbits near the perihelion, which is the closest distance to the Be star, naturally explains the unusual features of FRB 20201124A observed by FAST.
Astronomers have offered other different views on the formation mechanism of fast radio bursts. Professor Avi Loeb, an astronomer at Harvard University, believes that such strong and recurring radio signals may be sent by advanced extraterrestrial civilizations. If this is the case, should we reply?
First of all, for the signal FRB 20201124A, we currently do not have the ability to reply because its source is too far away from Earth, that is 1.3 billion light-years, even just to travel the distance will take up to 1.3 billion years. Sending the signal to such a distant place and still be received requires extremely high power signal transmitters, which humans are currently unable to do.
In addition, in the opinion of some astronomers, including Stephen Hawking, active contact with alien civilizations could be very dangerous, because once advanced alien civilizations are aware of the existence of Earth and they are able to come to our solar system, the huge difference in technological level, which may be greater than the gap between humans and ants, will probably pose a great risk to humanity.
So even if we do receive a signal from an alien civilization, some astronomers think we shouldn't reply, and that keeping quiet may allow humans to better survive in a dangerous universe. Humans have previously taken the initiative to send radio signals to some planets in the galaxy, which has been met with some criticism.
 H. Xu, J. R. Niu, P. Chen, K. J. Lee, et al. A fast radio burst source at a complex magnetized site in a barred galaxy, Nature, 2022, 609, 685-688.
 F. Y. Wang, G. Q. Zhang, Z. G. Dai, K. S. Cheng, Repeating fast radio burst 20201124A originates from a magnetar/Be star binary, Nature Communications, 2022, 13, 4382.
Source: Mars Science - Sohu