The search for extraterrestrial life and its radio signals outside of our solar system is still yielding no results. It’s not through lack of trying, though, to find potential advanced civilizations.
In a recent search, stars a few hundred light-years from Earth were surveyed by Jean-Luc Margot of UCLA’s Earth, Planetary & Space Sciences Department. In a sample of “TESS Objects of Interest,” Margot and his team investigated for radio signs of advanced civilizations. The Transiting Exoplanet study Satellite (TESS) is conducting an all-sky study of neighboring stars and any potential planets they may contain.
Margot is the creator of the UCLA SETI project “Are Alone in the Universe?” It searches for signs of extraterrestrial civilizations and gathers data from radio transmissions that could help locate them. Margot’s team directed the Green Bank Telescope toward the TESS objects from 2020 to 2023 to collect radio waves coming from a particular area of space. The group made use of the scope’s L-band receiver, which scans a spectral range between 1.15 and 1.73 GHz. They assert that there may be a narrowband “window” where alien transmissions, if any, could be picked up.
Finding a “wow!” signal from another culture would be exciting. But this time, that didn’t take place. “Based on our observations, we found that there is a high probability (94.0-98.7%) that fewer than 0.014% of stars earlier than M8 within 100 pc host a transmitter that is detectable in our search,” the research team reported in a publication summarizing their findings. That is a rather firm inference that we are not receiving any cosmic “hello” messages from nearby stars.
What Methods Of Communication Across Space Would Advanced Civilizations Use?
A relatively new field of study is the search for signs of advanced civilizations on other planets. Midway through the 20th century, the first searches started. Since then, utilizing the existing radio telescopes, SETI astronomers have developed search methods. But it continues to deal with some physical facts.
It is hardly surprising that communicating over vast chasms of space is challenging. Of course, there is a lag in time. At the speed of light, it would take just over four years for us to transmit a greeting to Proxima Centauri. If there is life there, it would send a “Hi neighbor” message back to us at the speed of light. Of course, it takes another four or so years for our distance to grow. That is an eight-year connection-building period.
Also keep in mind that signals must travel through any “stuff” that may be present in space, like as gas and dust. Some radiation types are absorbed by those. However, radio signals are a wonderful option for an interstellar greeting because they travel through space very effectively. The next thing to think about is what frequencies to employ. Due to the fact that they avoid the galaxy’s “hum” at lower frequencies, those between 1 and 10 GHz turn out to be highly useful. Higher frequencies can be drowned out by our atmosphere and likely the atmospheres of other worlds.
Astronomers therefore presume that a technologically advanced society may also utilize that range. Of course, there are also linguistic and cultural biases that would influence any communications. However, at least having a frequency range aids in starting the search.
What the Team Did
Margot’s team reasoned that they would need to sample for emissions produced by technologically advanced beings as part of their SETI search. “The search for technosignatures offers an opportunity to obtain reliable detections with clear interpretations,” they said. A narrowband signal from an emitter beyond the Solar System (say, 10 Hz at gigahertz frequencies) serves as an illustration of such a technosignature. These signals cannot be produced by natural environments, thus the discovery of one would be sufficient proof of the existence of another civilization.
They so sought to omit spontaneous emissions from the sample. Those would be radio waves produced by things and events that occur in nature. For instance, Jupiter in our own Solar System emits a lot of radio waves. Additionally, the Sun and Earth do as well, but we can easily omit them. Pulsars, star-forming regions, and supernova remnants are among the objects that emit powerful signals outside of the Sun and planets. Naturally, there are also extremely active emitters, like quasars and the areas near black holes. Any surveys looking for techno-signatures must exclude all of those sources.
So, between 5,385 and 18,173 light-years away, approximately 11,680 stars and associated planetary systems were detected by the GBT. On April 22,202, April 28, 2021, May 22, 2022, and May 13, 2023, the observations took place over two-hour sessions. They conducted two 2.5 minute scans on certain pairs of sources. The data, which comprised around 37 million narrowband emission detections, was then processed. This led to the conclusion that no adjacent advanced civilizations are using those frequencies for transmission.
Are We Alone? Crowdsourcing the Search
The “Are We Alone in the Universe?” initiative, run by Margot and his team, also includes citizen scientists from all over the world in their search. More than 10,000 people contributed more than 300,000 classifications of radio signals sent in from the neighboring community.
In addition, Margot provides graduate students at UCLA with a SETI course. Participants receive training in data collection and analysis from radio telescopes used in the hunt. The investigation of the various fields involved in the hunt for extraterrestrial intelligence is eye-opening. They involve knowledge of data collection, statistics, data science, telecommunications, and signal processing.
Even while the most recent signals search turned up no signs of modern civilizations in the vicinity of Earth, it does provide an essential message: if they’re “out there,” they’re not represented in that sampling. The absence of a convincing signal is just as significant as one, as is the case in much of science. It researchers must first discriminate between signals from space and signals from Earth-based technology. The process of separating things out is crucial to any search paradigm.
The team was able to improve its data pipelines and processing algorithms as a result of the entire project. That will be helpful if and when a signal is discovered in the future that might point to the existence of intelligent life in the universe. Additionally, there is still a great deal of sky to search for technologically advanced civilizations.
More info: A Search for Technosignatures Around 11,680 Stars with the Green Bank Telescope at 1.15-1.73 GHz (PDF)
UCLA SETI: Are We Alone in the Universe?
