Ever since American astronomer Frank Drake launched the first scientific experiment to search for radio signals from intelligent civilizations in 1960, the prevailing belief has been that scientists have examined only a very small percentage of the stars in our galaxy, which contains approximately 100 billion stars. This estimate has consistently been used to explain the lack of any evidence for extraterrestrial civilizations.
But a recent study suggests that reality may be different, indicating that the SETI (Search for Extraterrestrial Intelligence) program may have detected a number of stars that exceed previous estimates by tens of times, without researchers realizing it.
Scientists have discovered thousands of planets beyond our solar system. So where are all the aliens?
The study is led by Louisa Mason, a researcher at the University of Manchester, who re-evaluated historical radio observation data using a sophisticated model to simulate the distribution of stars in the Milky Way galaxy.
Millions of stars were within the field of observation
Mason relied on the Besançon model of the galaxy, a scientific computer model that simulates the entire structure of the Milky Way galaxy and predicts the distribution and properties of stars in any direction of the sky, and then compared it with data from observations made by the Green Bank Telescope in the United States and the Parkes Telescope in Australia.
Traditional calculations indicated that these 1,327 observations encompassed only about 288,000 stars, based on known star catalogs. However, the new model revealed that the telescopes were actually receiving signals from over 6.1 million stars, because the telescope's field of view also includes a vast number of faint stars that do not appear in conventional optical catalogs.
The antennas of the ALMA observatory in Chile, one of the most powerful radio observatories for studying the universe (European Southern Observatory).
“One of the most exciting results is that we realized we had detected far more stars than we thought we would,” Louisa Mason said in an official press release. “Even a small observation can contain a huge and diverse number of stars that we hadn’t originally intended to study.”
Why haven't we found a signal yet?
Despite the large number of stars that have been monitored, researchers emphasize that this does not mean that the chances of discovering intelligent civilizations have decreased.
Most stars were only observed for short periods, and the searches were limited to a narrow range of radio frequencies. Therefore, a signal may have been emitted while the telescope was not observing, or at a frequency completely different from those scientists were listening for.
For decades, research programs have focused on a frequency band known as the "water hole" because it lies between two frequencies associated with hydrogen and hydroxyl, the two basic components of the water molecule. This band also penetrates the Earth's atmosphere easily, making it the preferred choice for research operations since the 1960s.
Opening a new window in the sky
Mason did not just recalculate the number of stars, but also conducted the first research of its kind using data from the Atacama Millimeter and Submillimeter Array in Chile, which operates at higher frequencies than most conventional radio telescopes.
The researcher did not conduct new observations, but rather reanalyzed stored data in search of narrow-range signals that may have gone unnoticed.
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