Given the vastness of outer space, it seems unlikely that we will ever be able to find signs of alien life in the form of signals or radio messages.
However, it is possible that in fact we often receive messages from aliens, we are just looking for them in the wrong place. In addition, we may not pick up these signals, because we perceive them incorrectly. Some wonder if pulsars - rapidly rotating neutron stars that periodically emit radiation - could be the source of alien messages?
The SETI Institute in California is the world's leading organization for the search for alien civilizations in space. To this end, SETI has tried various methods. It currently uses the Allen antenna array, which has been monitoring radio waves from space since October 2007.
Recently, no signals have been recorded that could be sent by intelligent beings. Astrophysicist Gregory Benforl of the University of California, Irvine and his brother physicist James Benford believe that failures can be caused by the wrong approach, and not because the equipment is not good enough.
The brothers, as well as James' son Dominic, a NASA scientist, suggested that SETI study direct broadcast signals rather than the narrowband radiation that SETI currently focuses on.
In other words, an advanced extraterrestrial civilization may have an interest in reducing costs and optimizing the efficiency of sending signals into space, just like we are on Earth. The brothers suggested that alien signals might not be long-term and broadcast in all directions, but pulsating and narrow-frequency in the range of 1-10 gigahertz. Benford's paper was published in Astrobiology in June 2010.
"Our grandfather used to say, 'Words are cheap and whiskey costs money," said James Benford, reports UCI News. "Sending signals is an expensive process, and transmitting signals over distances of many light years requires significant resources."
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In addition, the brothers advised focusing on the center of the Milky Way, where most of the stars in the Galaxy are located.
“The stars there are billions of years older than our Sun, which offers a better chance of contact with an advanced civilization than studying signals from the younger and empty edge of our galaxy,” says Gregory Benford, according to UCI News.
Of course, the issue of choosing the right space for observation is only part of the problem.
The signal from an alien civilization may be short-lived. Therefore, if our devices are not directed to the right point at the right moment, then we will miss the signal. In addition, even if we manage to capture such a temporary signal, it can be perceived as a natural phenomenon.
According to the brothers, extraterrestrial signals can be regular, similar to the flashes of a lighthouse at intervals of several days.
“We must learn to identify these signals,” they told Discovery News.
Pulsars are neutron stars with a mass several times greater than that of our Sun. They rotate very quickly and are a source of powerful radiation. Extraterrestrial signals using the "beacon principle" can be very similar to the radiation of these stars.
Pulsars were discovered by Jocelyn Bell Burnell and Anthony Hewish in 1967. The first observed pulsar was named LGM-1, short for little green men, and had a period of 1.33 seconds, writes Universe Today. Scientists initially decided that these were signals from an extraterrestrial civilization.
Probably the best candidates for possible alien signals are non-repeating pulsar-like signals, the brothers say. One such example is PSR J1928 + 15, which pulsed for two minutes in 2005 and then suddenly stopped. It was recorded by the Arecibo telescope. They believe it could be an extraterrestrial signal, Discovery News reports.
Arecibo Observatory in Puerto Rico
The source of the pulsation was located at a distance of 26,000 light years somewhere near the center of the galaxy, its power was 190,000 terawatts (10,000 times more than all the energy required for human civilization). Some scientists believe that it was not actually radiation from a pulsar, but the consequences of an asteroid falling on a star, which violated its magnetic field.
There are a few more points to consider. For example, we assume that an advanced extraterrestrial civilization uses radio signals, but it can use a more advanced form of communication that is not yet available to our understanding and technology.
In turn, a civilization at our level of development can really use the method of sending signals described by the Benford brothers. But for such signals to reach Earth, they would have to travel many light years. Moreover, they will not contain any specific message, but just a kind of message: "We are there."
In addition, a controversial issue remains how many advanced life forms can exist in our galaxy, and what level of technological development they have reached. Given the huge number of stars in our galaxy (according to NASA, about 200 billion), there are many options, and the information available is limited. Until we manage to establish contact with these civilizations, we can only guess.