The search for extraterrestrial life has always been hampered by the strong background noise that the Earth generates, which makes it difficult to isolate alien signals. However, a new method of recognizing radio signals traveling through the Universe can greatly simplify this search.
“I think this is one of the biggest achievements of SETI in the recent period,” says astrophysicist Andrew Simion, co-author of an article describing this method and director of the Research Center for the Search for Extraterrestrial Intelligence (SETI) at Berkeley.
Radio waves emitted by alien civilizations that exist on the far edges of the Milky Way must travel 100 thousand light-years to reach Earth. These radio waves are scattered when they collide with the turbulent, ionized plasma of interstellar space. Such scattering is typical only for interstellar wanderings and was previously observed among pulsars. This creates a characteristic “flicker” known as “diffraction scintillation” when radio waves begin to interact with each other.
Bryan Brzycki, PhD in astrophysics, together with Simion and other colleagues from the SETI Breakthrough Listen project, have developed a program that allows distinguishing radio waves from this interstellar flicker. The scientist jokingly calls it “sifting out of a pile of hay.”
How to distinguish noise from a message?
For decades, SETI has been exploring the sky, looking for radio waves that could only come from alien technology. Sometimes a strange frequency appears among the white noise of the Universe. At these moments, the researchers, having gained patience, are trying to turn the radio from static mode into a player mode. In a very narrow frequency range, a clear and continuous signal appears, similar to the one that can be observed when receiving input signals from an FM radio or a spacecraft.
Natural phenomena such as lightning, the Sun, pulsars and supernovae cannot create such narrow signals because they have a much larger frequency range.
However, although there are reasons to treat these signals with suspicion, most of them are bursts created by human intervention, such as satellites, mobile phones, Wi-Fi, or microwave ovens.
For example, the origin of the famous 72-second SETI Wow signal, discovered in 1977 by a radio telescope in Ohio, is still unknown. Although some hypotheses associate it with a comet. After that time, the signal was no longer registered.
Scintillation as a way of communication
In order to be sure that they receive signals from alien civilizations and not from terrestrial sources, SETI explores the sky to determine the directions from which the signals come. If the signal comes from several directions, it is probably due to terrestrial interference. But if it comes from one direction, it may be a message from aliens.
However, the answer to the existential question of whether we are alone in the Universe may not satisfy us. We need to be absolutely sure. If aliens exist, there is a high probability that they also use radio waves for communication, since this is an effective way of communication that easily penetrates the atmosphere and interstellar space, according to the researchers.
It is assumed that an advanced alien civilization would understand that “scintillation itself is a message,” the researchers write. Even if the narrowband radio signal does not contain explicit initial data after traveling through interstellar space, the team concludes that the very presence of scintillation would have conveyed the message: “we’re here”.
Earlier we reported on how scientists were preparing a plan for “first contact” with aliens.
According to The Astrophysical Journal
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