Do signals from alien civilizations pass by Earth without us noticing them? | sciences

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In one of the most exciting issues in modern astronomy, scientists have been trying for decades to answer a question posed by Italian physicist Enrico Fermi in 1950: If the universe is full of habitable planets, where are everyone? Today, a new study suggests that the problem may not be the absence of intelligent civilizations, but rather the way we search for them.

Researchers from the SETI Institute have found that radio signals from potential alien civilizations may be distorted and stretched by the space weather surrounding their stars, making them almost invisible to current monitoring devices on Earth.

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Signs may already exist

For years, astronomers have been searching for what are known as narrowband radio signals, which are highly concentrated signals that appear as sharp peaks in the radio spectrum and are not produced by known natural processes.

“Signals like this do not occur naturally, so detecting a very narrow signal would be a strong indicator of the presence of an interesting source,” said astronomer Ivan Kane of Trinity College Dublin, who was not involved in the study.

An illustration of an exoplanet in an alien star system. New research suggests that radio emissions from intelligent aliens may be transformed by the plasma from their home stars — suggesting scientists could be overlooking evidence of extraterrestrial intelligence. (Image credit: NASA/JPL-Caltech/R. Hurt, K. Miller (Caltech/IPAC))
An imaginative drawing of an exoplanet orbiting a distant star, showing how star plasma might distort the signals of potential intelligent civilizations before they reach Earth (California Institute of Technology)

Scientists give the example of rovers on Mars, as their signals can be easily distinguished if they are monitored from appropriate astronomical distances, because they carry a clear artificial fingerprint that differs from natural radiation.

But despite decades of research, scientists have yet to find any confirmed signal of non-human origin.

Star weather may erase traces of civilizations

The study published in The Astrophysical Journal suggests that the problem may lie in the environment surrounding the stars themselves. Space weather refers to the flows of charged particles, radiation, and plasma emissions released by stars, such as the solar wind and coronal ejections from our Sun.

The study was led by astronomer Vishal Ghajar of the SETI Institute in collaboration with researcher Grace Brown. The team studied the impact of space weather on historical communications between Earth and spacecraft such as Mariner 4 and the Viking probes.

A planet's radio signal may begin as a sharp tone (left, white) but can be spread out by the star's plasma winds into a wider, fainter signal (right, green). The new study suggests radio astronomers may be missing signals by mostly looking for the sharp white shape instead of the broader green one. (Image credit: Vishal Gajjar)
Illustration showing how plasma winds around stars can distort potential radio signals from intelligent civilizations and make them more difficult to detect from Earth (Ghaggar)

By analyzing one of the largest databases of radio signal distortion, the researchers were able to simulate what would happen to a signal from an advanced civilization orbiting a distant star.

Maybe we’re looking for the wrong shape

The results show that a radio signal may start out as a narrow, clear pulse, but expand and spread across a wider range of frequencies as it passes through the stellar plasma.

This expansion leads to the signal energy being distributed over a larger frequency area, making it appear much weaker than it originally is, and may fall below the detection limits of current telescopes.

“If the signal is distorted by the environment around its star, it may fall below our detection threshold even though it is already there, which may help explain the silence we have encountered in technical signal searches,” Vishal Gajjar said.

Radio signals from potential alien civilizations may be distorted by plasma and space weather around their stars (Al Jazeera/generated by artificial intelligence)
Highly concentrated signals that appear as sharp peaks in the radio spectrum and are not produced by known natural processes (Al Jazeera/generated by artificial intelligence)

In other words, some civilizations may indeed be broadcasting their signals, but scientists are focused on looking for sharp, focused signals when in reality they reach us in a broader, more widespread form.

Red dwarfs are in the spotlight

The researchers focused in particular on red dwarf stars, which are the most common type of star in our galaxy, making up about three-quarters of the Milky Way’s stars.

Scientists believe that some of these stars date back to the very early stages of the history of the universe, giving their planets enough time to develop life and perhaps technical civilizations.

Therefore, these star systems may become prime targets for future research, with the development of new algorithms capable of identifying distorted signals instead of just the traditional narrow ones.



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