Radio signals unlikely to be extragalactic aliens saying 'hi'

Astronomers have detected ultra-brief repeating energy bursts from deep space for only the second time in history, with some suggesting they could be evidence of advanced alien life. Several researchers shared their views with China Daily writers Zhang Zhouxiang and Wang Yu:

Shi Hao, a researcher of space technology

Even if there is the possibility an extraterrestrial civilization sent the fast radio bursts (FRB), the distance to us is beyond the reach of any technology we can image.

A little comparison will explain how far away the origin of the signal is from us. The average distance from the Earth to the sun is called an Astronomical Unit (AU), and it takes light from the sun about eight minutes to reach the Earth.

Voyager 1, humanity's farthest spacecraft that started in 1977, is now 145 AU from the Earth after 42 years of travelling, yet that's only 0.23 of one light-year.

It would take more than over 17000 years for Voyager 1 to travel one light-year, and the distance to the origin of the FRB is 1.5 billion times that.

From a large perspective, some scientists believe the radius of the universe is 13.7 billion light-years; The FRB signal this time has travelled about one ninth of that to reach us.

Ge Jian, an astronomy professor at the University of Florida

The origin of the FRB is far from us, not only in terms of space, but also in terms of time. More exactly speaking, in the study of the universe, we use light travel time to measure distance, time can represent distance.

In other words, the signal of the FRB was sent at least 1.5 billion years ago, and the Earth then was still in Proterozoic Eon on its geological chronology. There were no dinosaurs on the Earth then. It was mainly occupied by ancient algae and bacteria, and it would take another 2.8 billion years for dinosaurs to appear.

With more wide-field radio telescopes being put into use in the future, scientists are expected to observe more similar FRBs and solve the mystery.

Gou Lijun, a research professor at the National Astronomical Observatories, Chinese Academy of Sciences

Fast Radio Bursts are a rather new concept in astronomical studies. It was discovered by accident in 2007 from the SMC archival data by Professor Duncan Lorimer at West Virginia University. Afterwards, within the following five years astronomers did not detect any more, and started to doubt their existence. Until 2012, when another FRB was finally observed, the doubt finally disappeared. Although dozens of events have been observed, astronomers still have no idea about the cause of the events.

Yuan Lanfeng, an associate professor at University of Science and Technology of China.

On micro blogs and other social media platforms, readers have been associating the signal with the famous science fiction The Three-body Problem, in which the Earth replied to a signal from the space and faced the threat of invasion from the latter. That's why many readers jokingly write "Don't answer!" three times on micro blog, which is a famous scenario of the novel.

Their concern is understandable. However, even if you hope to answer the signal, there is no way of doing that with our current technology.

Yu Jun, a senior editor on space at pop-science website guokr.com

The long distance means a high attenuation rate. In other words, the burst at the origin of the signal must be extremely powerful so that we can receive it. There is no way to calculate the exact amount of energy needed this time, but we can compare it to the sun: It is like bursting out the energy radiated by the sun for dozens to tens of thousands of years within 0.01 second.

Since the discovery of the first FRB in 2007, humans have only observed about 60 of them. As a result of insufficient observation data, there is no confirmed theory on what phenomenon produced them.

However, considering the extremely high amount of energy they need, the number of "suspects" is limited, too. According to existing theories, there are at least several possible causes of FRBs, such as the merging of black holes or neutron stars, hyperflares of magnetars, especially energetic supernova, or the collapse of the magnetospheres of Kerr–Newman black holes.

Strictly speaking, the possibility of a super extraterrestrial civilization sending such a signal cannot be excluded, but the possibility is really low considering the high amount of energy needed. Besides, there is no evidence leading specifically to this possibility. So there is no need to exaggerate it.

Copyright: China Daily/ Asia News Network