In 1960, Freeman Dyson proposed how advanced civilizations could create megastructures that enclosed their star, allowing them to harness all of their star’s energy and multiplying the habitable space they could occupy. In 2015, the astronomical community was intrigued when the star KIC 8462852 (aka. Tabby’s Star) began experiencing unexplained changes in brightness, leading some to speculate that the variations might be due to a megastructure. While the final analysis of the star’s light curve in 2018 revealed that the dimming pattern was more characteristic of dust than a solid structure, Tabby’s Star focused attention on the subject of megastructures and their associated technosignatures.
Dyson’s ideas were proposed at a time when astronomers were unaware of the abundance of exoplanets in our galaxy. The first confirmed exoplanet was not discovered until 1992, and that number has now reached 5,514! With this in mind, a team of researchers from Bangalore, India, recently released a paper that presents an alternative to the whole megastructure concept. For advanced civilizations looking for more room to expand, taking planets within their system – or capturing free-floating planets (FFP) beyond – and transferring them into the star’s circumsolar habitable zone (HZ) is a much simpler and less destructive solution.
Life on Earth is a glorious dance of data. From the songs of backyard birds to the chemical exchanges of forest trees, the exchange of information between living things is an essential part of its existence and evolution. Humans, too, are a part of that dance, with friendship chats over morning coffee, bold headlines in newspapers, and TikTok videos of teenagers. Right now human data is just one part of Earth’s living data exchange, but it could soon become the overwhelming dominant part. If the same is true for all advanced civilizations, it could impact our search for alien life.
From June 18th to 22nd, the Penn State Extraterrestrial Intelligence Center (PSETI) held the second annual Penn State SETI Symposium. The event saw experts from many fields and backgrounds gathering to discuss the enduring questions about SETI, the technical challenges of looking for technosignatures, its ethical and moral dimensions, and what some of the latest experiments have revealed. Some very interesting presentations examined what will be possible in the near future and the likelihood that we will find evidence of extraterrestrial intelligence.
Among them, there were some very interesting presentations by Adam Frank, Professor of Astrophysics at the University of Rochester; Ph.D. student Matias Suazo, an astrophysicist and member of Project Haephestos at the University of Uppsala; and Nicholas Siegler, the Chief Technologist of NASA’s Exoplanet Exploration Program (ExEP). These presentations addressed ongoing issues in the search for extraterrestrial intelligence (ETI), technosignatures, the role of oxygen in the evolution of complex life, and what motivations extraterrestrial civilizations (ETC) might have for creating noticeable signatures.
In a recent study published in The Astronomical Journal, a researcher from the École Polytechnique Fédérale de Lausanne (EPFL) discusses the potential reasons why we haven’t received technoemission, also called technosignatures, from an extraterrestrial intelligence during the 60 years that SETI has been searching, along with recommending additional methods as to how we can continue to search for such emissions.
This naturally raises the all-important question: are we going about the business of SETI wrong? Instead of looking for technosignatures within our galaxy, as all previous SETI surveys have done, should we look for activity beyond our galaxy (from possible Type II and Type III civilizations)? This premise was explored in a recent paper led by researchers from the National Chung Hsing University in Taiwan. Using data from the largest SETI project to date, Breakthrough Listen, the team looked for potential radio technosignatures from extragalactic sources.
If life is common in our Universe, and we have every reason to suspect it is, why do we not see evidence of it everywhere? This is the essence of the Fermi Paradox, a question that has plagued astronomers and cosmologists almost since the birth of modern astronomy. It is also the reasoning behind the Hart-TIpler Conjecture, one of the many (many!) proposed resolutions, which asserts that if advanced life had emerged in our galaxy sometime in the past, we would see signs of their activity everywhere we looked. Possible indications include self-replicating probes, megastructures, and other Type III-like activity.
On the other hand, several proposed resolutions challenge the notion that advanced life would operate on such massive scales. Others suggest that advanced extraterrestrial civilizations would be engaged in activities and locales that would make them less noticeable. In a recent study, a German-Georgian team of researchers proposed that advanced extraterrestrial civilizations (ETCs) could use black holes as quantum computers. This makes sense from a computing standpoint and offers an explanation for the apparent lack of activity we see when we look at the cosmos.
For over sixty years, astronomers and astrophysicists have been engaged in the Search for Extraterrestrial Intelligence (SETI). This consists of listening to other star systems for signs of technological activity (or “technosignatures), such as radio transmissions. This first attempt was in 1960, known as Project Ozma, where famed SETI researcher Dr. Frank Drake (father of the Drake Equation) and his colleagues used the radio telescope at the Green Bank Observatory in West Virginia to conduct a radio survey of Tau Ceti and Epsilon Eridani.
Since then, the vast majority of SETI surveys have similarly looked for narrowband radio signals since they are very good at propagating through interstellar space. However, the biggest challenge has always been how to filter out radio transmissions on Earth – aka. radio frequency interference (RFI). In a recent study, an international team led by the Dunlap Institute for Astronomy and Astrophysics (DIAA) applied a new deep-learning algorithm to data collected by the Green Bank Telescope (GBT), which revealed eight promising signals that will be of interest to SETI initiatives like Breakthrough Listen.
The Five-hundred-meter Aperture Spherical Telescope (FAST), located in China, is currently the world’s largest and most sophisticated radio observatory. While its primary purpose is to conduct large-scale neutral hydrogen surveys (the most common element in the Universe), study pulsars, and detect Fast Radio Bursts (FRBs), scientists have planned to use the array in the Search for Extraterrestrial Intelligence (SETI). Integral to this field of study is the search for technosignatures, signs of technological activity that indicate the presence of an advanced civilization.
While many potential technosignatures have been proposed since the first surveys began in the 1960s, radio transmissions are still considered the most likely and remain the most studied. In a recent survey, an international team of SETI researchers conducted a targeted search of 33 exoplanet systems using a new method they call the “MBCM blind search mode.” While the team detected two “special signals” using this mode, they dismissed the idea that they were transmissions from an advanced species. Nevertheless, their survey demonstrated the effectiveness of this new blind mode and could lead to plausible candidate signals in the future.
The Robert C. Byrd Green Bank Telescope (GBT), part of the Green Bank Observatory in West Virginia, is the world’s premiere single-dish radio telescope. Between its 100-meter dish (328-foot), unblocked aperture, and excellent surface accuracy, the GBT provides unprecedented sensitivity in the millimeter to meter wavelengths – very high to extremely high frequency (VHF to EHF). Since 2017, it also became one of the main instruments used by Breakthrough Listen and other institutes engaged in the Search for Extraterrestrial Intelligence (SETI).
Recently, an international team of researchers from the SETI Institute, Breakthrough Listen, and multiple universities scanned twelve exoplanets for signs of technological activity (aka. “technosignatures”). Their observations were timed to coincide with the planets passing in front of their sun relative to the observer (i.e., making a transit). While the survey did not detect any definitive evidence of technosignatures, they did identify two radio signals of interest that warrant follow-up observation. This new technique could vastly expand the field of SETI and create all kinds of opportunities for future research.
According to new research led by the Advanced Propulsion Laboratory at Applied Physics (APL-AP), GWs could also be used in the Search for Extraterrestrial Intelligence (SETI). As they state in their paper, LIGO and other observatories (like Virgo and KAGRA) have the potential to look for GWs created by Rapid And/or Massive Accelerating spacecraft (RAMAcraft). By combining the power of these and next-generation observatories, we could create a RAMAcraft Detection And Ranging (RAMADAR) system that could probe all the stars in the Milky Way (100 to 200 billion) for signs of warp-drive-like signatures.