What happens when one galaxy shoots a bigger galaxy right through the heart? Like a rock thrown into a pond, the smashup creates a splash-up of starry ripples. At least that’s what happened to the Bullseye galaxy, which is the focus of observations made by NASA’s Hubble Space Telescope and the Keck Observatory in Hawaii.
In a study published today by The Astrophysical Journal Letters, a research team led by Yale University’s Imad Pasha identifies nine visible ring-shaped ripples in the structure of the galaxy, formally known as LEDA 1313424. The galaxy is 567 million light years from Earth in the constellation Pisces.
The Bullseye now holds the record for the most rings observed in a galaxy. Previous observations of other galaxies showed a maximum of two or three rings.
“This was a serendipitous discovery,” Pasha said in a news release. “I was looking at a ground-based imaging survey and when I saw a galaxy with several clear rings, I was immediately drawn to it. I had to stop to investigate it.”
Eight separate rings could be spotted in the image captured by Hubble’s Advanced Camera for Surveys. The ninth ring was identified in data from the Keck Observatory. Follow-up observations also helped the team figure out which galaxy plunged through the Bullseye’s core. It’s the blue dwarf galaxy visible to the center-left of LEDA 1313424 in the Hubble image.
This illustration pinpoints the nine rings in the Bullseye galaxy. Credit: NASA, ESA, Ralf Crawford (STScI)
Researchers say the current view captures the state of the Bullseye about 50 million years after the blue dwarf blasted through its core. Even though the two galaxies are separated by 130,000 light-years, a thin trail of gas still links them together. “We’re catching the Bullseye at a very special moment in time,” said Yale Professor Pieter G. van Dokkum, a study co-author. “There’s a very narrow window after the impact when a galaxy like this would have so many rings.”
The multi-ringed shape conforms to the mathematical models for a headlong galaxy-on-galaxy collision. The blue dwarf’s impact caused galactic material to move both inward and outward, sparking multiple waves of star formation along the lines of the ripples — almost exactly as the models predicted.
“It is immensely gratifying to confirm this longstanding prediction with the Bullseye galaxy,” van Dokkum said.
The models suggest that the first two rings in the Bullseye formed quickly and spread out in wider circles. The timing for the formation of additional rings was staggered as the blue dwarf plowed through the bigger galaxy’s core. The research team suspects that there was once a 10th ring to the galaxy, but that it faced out and is no longer detectable. That ring might have been as much as three times farther out than the widest ring seen in the Hubble image.
This artist’s conception shows our Milky Way galaxy at left, and the Bullseye galaxy at right. Credit: NASA, ESA, Ralf Crawford (STScI)
Compared to our own Milky Way galaxy, the Bullseye is a big target. It’s about 250,000 light-years wide, as opposed to 100,000 light-years for the Milky Way.
Billions of years from now, the Milky Way and the neighboring Andromeda galaxy are due to collide, but computer simulations suggest that the dynamics of that collision will be more complex than merely dropping a cosmic rock into a pond, or shooting an arrow through a bull’s-eye.
Fortunately, astronomers won’t have to wait billions of years to see more spot-on galactic collisions. “Once NASA’s Nancy Grace Roman Space Telescope begins science operations, interesting objects will pop out much more easily,” van Dokkum said. “We will learn how rare these spectacular events really are.”
At first glance the large scale structure of the Universe may seem to be a swarming mass of unconnected galaxies. Yet somehow, they are! The ‘cosmic web’ is the largest scale structure of the Universe and consists of vast networks of interconnected filamentary structures that surround empty voids. A team of astronomers have used hundreds of hours of telescope time to capture the highest resolution image ever taken of a single cosmic filament that connects to forming galaxies. It’s so far away from us that we see it as it was when the Universe was just 2 billion years old!
Dark matter is largely invisible to us, only detectable through its interaction with other phenomenon. It makes up about 85% of the matter in the universe and plays a crucial role in shaping the large-scale structure of the cosmos. It doesn’t emit, absorb, or reflect light hence its name and its gravitational influence holds galaxies together and forms the cosmic web—a vast, interconnected network of filaments composed of dark matter, gas, and galaxies. Scientists have been studying the cosmic web using simulations and gravitational lensing techniques to understand the nature of dark matter and its role in evolution of the universe.
A massive galaxy cluster named MACS-J0417.5-1154 is warping and distorting the appearance of galaxies behind it, an effect known as gravitational lensing. This natural phenomenon magnifies distant galaxies and can also make them appear in an image multiple times, as NASA’s James Webb Space Telescope saw here. Two distant, interacting galaxies — a face-on spiral and a dusty red galaxy seen from the side — appear multiple times, tracing a familiar shape across the sky. NASA, ESA, CSA, STScI, V. Estrada-Carpenter (Saint Mary’s University).
One of the biggest challenges that faces astronomers studying the cosmic web is that the gas has mainly been detected through its absorption of light from a more distant object. The results of such studies however do not help us to understand the distribution of gas in the web. Studies that focus on hydrogen which is the most common element in the universe, can only be detected from a very faint glow so that previous attempts to map its distribution have failed.
In this new paper that was published by a team of researchers that were led by scientists from the University of Milano-Bicocca and included members from the Max Planck Institute for Astrophysics. The team employed the use of the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope at the European Southern Observatory in Chile. The instrument was designed to capture 3D data of astronomical objects by combining images and spectroscopic observations across thousands of wavelengths simultaneously. Even with the capabilities of MUSE, the team had to capture data over hundreds of hours to reveal sufficient detail in the filaments of the cosmic web.
ESO’s Very Large Telescope is composed of four Unit Telescopes (UTs) and four Auxiliary Telescopes (ATs). Seen here is one of the UTs firing four lasers which are crucial to the telescope’s adaptive optics systems. To the right of the UT are two ATs, these smaller telescopes are moveable and work in tandem with the other telescopes to create a unique and powerful tool for observing the Universe.
The team was led by PhD student at the University of Milano-Bicocca Davide Tornotti and they used MUSE to study a filament that measures 3 million light years in length. The filament connects two galaxies, each with a supermassive black hole deep in their core. They were able to demonstrate a new way of mapping the intergalactic filaments, helping to understand more about galactic formation and the evolution of the universe.
Before they were able to start collecting the data, the team were able to run simulations of the emissions from filaments based upon the current model of the universe. They were then able to compare the results and both were remarkably similar. The discovery can help us to learn how galaxies in the cosmic web are fuelled but the team assert that they still need more data. More structures are now being uncovered as the techniques are repeated with the goal to finally reveal how gas is distributed among the cosmic web.
Revelations from the past can seem quaint once we’ve been living with them for a generation or two. That’s true of the realization in the past that spawned SETI: the Search for Extraterrestrial Intelligence. Humanity realized that if we’re blasting radio signals out into the cosmos haphazardly, then other ETIs, if they exist, are probably doing the same.
It seems obvious now, but back then, it was a revelation. So, we set up our radio antennae and began scanning the skies.
The realization that other ETIs are probably sending out radio noise leads to the obvious question: How easily can hypothetical ETIs detect our radio signals and other technosignatures?
A fledgling space-travelling civilization similar to ours may be out there somewhere in the Milky Way. Maybe they have their own fledgling SETI program, complete with radiotelescope arrays scanning the sky for the telltale signs of another technological civilization.
If there is, and if they do, from how far away could they detect our technosignatures? New research is asking that question.
Nikola Tesla was one of the first to suggest communicating with beings on other planets. In 1899, Tesla thought he had detected a signal from Mars. In the early part of the 20th century, Guglielmo Marconi also thought he had heard signals from Mars. These potential signals were serious enough that when Mars was closest to Earth in 1924, the USA promoted a Radio Silence Day in order to better detect signals from Mars.
We know better now. The only signals we’ll detect will be from our own Martian rovers and orbiters. However, the basic idea of searching for radio signals from other worlds was planted, and people started taking it more seriously.
In 1971, NASA considered Project Cyclops, a plan to build an array of 1500 radio dishes to scan the cosmos for signals. Although it was never funded, it helped lead to the modern SETI.
It’s a simple matter to imagine that other civilizations followed a similar path and are now searching the sky for signals. In the new research in The Astronomical Journal, Sheikh and her co-researchers try to understand how one of these civilizations could detect our technosignatures if they had the same technology as we do in 2024.
“In SETI, we should never assume other life and technology would be just like ours, but quantifying what ‘ours’ means can help put SETI searches into perspective.”
Macy Huston, co-author, Dept. of Astronomy, UC Berkeley
This is important because similar research looks for advanced ETIs that are further along the Kardashev Scale, which many researchers think is probable. However, this means researchers have to do a lot of technological extrapolation. “In this paper, we instead turn our gaze Earthward, minimizing the axis of extrapolation by only considering transmission and detection methods commensurate with an Earth 2024 level,” the authors write.
It all boils down to simple questions: Can an ETI with our current technology detect our technosignatures? If the answer is yes, which of our signatures would they detect, and from how far away?
The researchers considered multiple types of different technosignatures, including radio transmissions, microwave signals, atmospheric technosignatures like NO2, satellites, and even city lights. They used a theoretical, modelling-based method in their effort, and they say they’re the first to analyze these technosignatures together rather than separately.
“Our goal with this project was to bring SETI back ‘down to Earth’ for a moment and think about where we really are today with Earth’s technosignatures and detection capabilities,” said Macy Huston in a press release. Huston is a co-author and postdoc at the University of California, Berkeley, Department of Astronomy. “In SETI, we should never assume other life and technology would be just like ours, but quantifying what ‘ours’ means can help put SETI searches into perspective.”
This table is a rough timeline of human technologies across different wavelengths and multimessenger approaches. Image Credit: Sheikh et al. 2025.
Imagine a hypothetical space probe travelling toward us from this hypothetical, technologically equivalent ETI. According to the researchers, the first technosignature they’d detect would come from our effort to detect potentially hazardous asteroids that might be headed for Earth. This is our planetary radar, like the signals coming from the now-defunct Arecibo Radio Observatory. These are detectable out to about 12,000 light years from Earth. That’s about the same distance away as the Tadpole Nebula.
The hypothetical space probe would have a long way to travel before it could detect our next technosignature. When it was about 100 light-years away, it would detect signals from NASA’s Deep Space Network that’s used to communicate with spacecraft we send out into the Solar System. 100 light-years away is about the same distance away as Alpha Pictoris, the brightest star in the Pictor constellation.
The alien spacecraft would hit paydirt at about four light-years away, around the same distance as our closest stellar neighbour, Proxima Centauri. At that distance, it would detect lasers, our atmospheric NO2 emissions, and even LTE signals.
The figure below illustrates how our current technology would detect our own technosignatures and at what distances.
This figure from the research shows the maximum distances that each of Earth’s modern-day technosignatures could be detected at using modern-day receiving technology. Image Credit: Sheikh et al. 2025.
“One of the most satisfying aspects of this work was getting to use SETI as a cosmic mirror: what does Earth look like to the rest of the galaxy? And how would our current impacts on our planet be perceived,” said Sheikh. “While, of course, we cannot know the answer, this work allowed us to extrapolate and imagine what we might assume if we ever discover a planet with, say, high concentrations of pollutants in its atmosphere.”
The research also illustrates how our own technosignature footprint is growing. According to the authors, it highlights “the growing complexity and visibility of the human impact upon our planet.”
It also shows that despite some second-guessing among the SETI community, it’s probably wise to focus our search on radio waves. “In this framework, we find that Earth’s space-detectable signatures span 13 orders of magnitude in detectability, with intermittent, celestially targeted radio transmission (i.e., planetary radar) beating out its nearest nonradio competitor by a factor of 103 in detection distance,” the authors write in their paper.
The authors also point out that we can begin to understand what an ETI might surmise about us based on our technosignatures. That can also serve as a mirror through which we can see ourselves. “It is possible for ETIs to hypothesize about our culture, society, biosphere, etc., from our unintentional technosignatures, and thinking through those possible hypotheses can help us interrogate how we are presenting ourselves to the galaxy: how we organize socially, how we relate to the world around us, how we perceive and experience things, and perhaps even what we value,” the authors explain in their research.
For example, they could correctly surmise that our species has no biological capacity to detect radio signals; otherwise, our world would be an unimaginably noisy cacophony of competing signals. Or, they may infer the reverse. “Conversely, our reliance on radio waves could make it natural for an alien species to wonder if it is because we can detect them biologically!” the authors write.
As in all things SETI and technosignature related, we’re left wondering.
However, with their “Earth detecting Earth” paradigm, Sheikh and her co-authors are at least giving us another way to examine one of our most quintessential questions: Are we alone?
It seems everyone is talking about the Moon and everyone wants to get their foot in the door with the renewed passion for lunar exploration. ESA too have jumped into the lunar landing game having just signed a contract with Thales Alenia Space to build its Argonaut Lunar Lander. Compared to other landers, it will be unique in its ability to handle the harsh night and day conditions on the lunar surface. Each mission is planned to have a 5 year life and will have a standard descent and cargo module but with different payloads determined by the Moon. If all goes to plan then the first lander will fly in 2031.
The Moon, Earth’s only natural satellite, is a celestial body that has fascinated us for centuries. It orbits Earth at an average distance of about 384,400 kilometres and is a barren, rocky surface covered in craters, mountains, and vast plains of solidified lava. Its lack of atmosphere results in extreme temperature fluctuations, with daytime temperatures reaching up to 127°C and nighttime temperatures plummeting as low as -173°C.
The occultation of Aldebaran by the Moon in 2016. Credit: Andrew Symes.
Since the Apollo missions of the 1960’s lunar exploration has become a central part of space science. The first major milestone was achieved in 1959 when the Soviet Luna 2 mission became the first human-made object to impact the Moon. This was followed by Luna 9, which successfully landed and transmitted images from the surface. This was followed by Apollo 11 and humanity’s first steps on another celestial body. Since then robotic missions like China’s Chang’e program, India’s Chandrayaan missions, and NASA’s Artemis program have aimed to study lunar water ice, geology, and sustainability for long-term human presence.
Apollo 11 launch using the Saturn V rocket
The European Space Agency have got in on the act now with their plans to build Argonaut, an autonomous lunar lander. It will launch on regular missions to the moon and can be used for delivering rovers, infrastructure, instrumentation or resources to the Moon for lunar explorers. The lander will compose of the descent module, the payload and the cargo platform which will act as the interface between the lander and the payload and will integrate operations between the two.
ESA signed their contract with Thales Alenia Space in Italy, a joint venture and prominent player in the global space market. They have been delivering high-tech solutions for navigation, telecommunication and Earth observation for over 40 years. They will be leading the European group to build the descent module with the remaining core team from the Group’s UK and France.
Artist’s impession of the Lunar Gateway with the Orion spacecraft docked on the left side. Credit: ESA
Once complete, Argonaut will become a key part of ESA’s lunar exploration strategy and will integrate with their Lunar Link on the new lunar Gateway. This new international space station is planned to orbit the Moon as part of the NASA Artemis programme. Argonaut will become one of Europe’s main contributions to international lunar exploration as nations work together to establish permanent presence on our nearest celestial neighbour.
We can’t help ourselves but wonder about life elsewhere in the Universe. Any hint of a biosignature or even a faint, technosignature-like event wrests our attention away from our tumultuous daily affairs. In 1984, our wistful quest took concrete form as SETI, the Search for Extraterrestrial Intelligence.
Unfortunately, or maybe fortunately, SETI has turned up nothing. Recently, scientists used a powerful new data system to re-examine data from one million cosmic objects and still came up empty-handed. Did they learn anything from this attempt?
This effort used COSMIC, which stands for Commensal Open-Source Multimode Interferometer Cluster. It’s a signal-processing and algorithm system attached to the Karl G. Jansky Very Large Array (VLA) radio astronomy observatory. According to SETI, it’s designed to “search for signals throughout the Galaxy consistent with our understanding of artificial radio emissions. “
Modern astronomy generates vast volumes of data and algorithms and automated processing are needed to comb through it all. So far, COSMIC has observed more than 950,000 objects, and the results of the effort are in a new paper. It’s titled “COSMIC’s Large-Scale Search for Technosignatures during the VLA sky Survey: Survey Description and First Results” and will be published in The Astronomical Journal. The lead author is Chenoa Tremblay from SETI.
Image of radio telescopes at the Karl G. Jansky Very Large Array, located in Socorro, New Mexico. Image Credit: National Radio Astronomy Observatory
“The place of humanity in the Universe and the existence of life is one of the most profound and widespread questions in astronomy and society in general,” the authors write. “Throughout history, humans have marvelled at the starry night sky.”
In our modern technological age, we marvel not only with our eyes but with powerful telescopes. The Karl G. Jansky Array is one of those telescopes, though it’s actually 28 radio dishes working together as an interferometer. Each one is 25 meters across, and they’re all mounted on movable bases that are maneuvered around railway tracks. This gives the system the ability to change its radius and density so it can balance its angular resolution and its sensitivity.
The Array is used to observe astronomical objects like quasars, pulsars, supernova remnants, and black holes. It’s also used to search trillions of systems quickly for signs of radio transmissions.
Currently, the VLA is engaged in the VLA Sky Survey (VLASS), a long-term effort to detect transient radio signals in the entire visible sky. The elegance of the COSMIC system is that it can “tag along” as VLASS progresses. “COSMIC was designed to provide an autonomous real-time pipeline for observing and processing data for one of the largest experiments in the search for extraterrestrial intelligence to date,” the authors write.
One of the problems facing modern astronomy is the deluge of data. There aren’t enough astronomers or students to possibly manage it. “The idea is that we are receiving increasing quantities of data that must be sorted in new ways in order to find information of scientific interest,” the authors write. “Developing algorithms to search through data efficiently is a challenging part of searching for signs of technology beyond our solar system.”
There aren’t enough human brains to manage the tidal wave of valuable data created by modern astronomy. The signals we seek are buried in this wave, and we need automated help to find them. Image Credit: DALL-E
COSMIC is a digital signal processing pipeline that VLASS data flows through. It searches for signals that display temporal and spectral characteristics consistent with our idea of what an artificial technological signal would look like.
The sky is full of radio signals from astrophysical objects. In order for a signal to be considered a technosignature, it needs to be a narrowband signal, and its frequency should change over time as a result of the Doppler effect. That still leaves potentially millions of hits. Researchers are forced to make other assumptions about what might constitute a technosignature, and COSMIC filters through signals based on those assumptions. “In this pipeline, extraterrestrial technosignatures are characterized by a set of assumptions and conditions that, if not met, are used to eliminate hits that do not meet these assumptions,” Tremblay and her co-authors write. “The output of this search is a database of “hits” and small cutouts of the phase-corrected voltage data for each antenna around the hits called “postage stamps.”
COSMIC examined more than 950 million objects in space for technosignatures and found nothing. But that’s okay. SETI scientists still learned things from the effort by testing their system.
“As shown in <Figure 15>, within the last 11 months of operation, COSMIC has observed over 950,000 fields and is rapidly becoming one of the largest SETI experiments ever designed,” the authors write.
Figure 15 from the paper shows a plot in galactic coordinates of all the coordinates currently in the database observed from 29 March 2023 to 14 July 2024. The orange points represent data from
frequencies below 4 GHz (S-band), and the blue points are from data collected above 4 GHz (C-band). Image Credit: Tremblay et al. 2025.
Though COSMIC has observed almost 1 million sources, researchers focused on a small subset to rigorously test the postprocessing system. In a test field of 30 minutes of data, they searched toward 511 stars from the Gaia catalogue. “In this search, no potential technosignatures were identified,” the authors write.
However, this is just the beginning and constitutes a successful test of the system. Future efforts with COSMIC will be both faster and more automated, which is necessary to manage the vast volume of data in modern astronomy.
“This work overall represents an important milestone in our search,” the authors write in their paper’s conclusion. “With the rapidly growing database, we need new methods for sorting through the data, and this paper describes a rapid and viable filtering mechanism.”
When we first began searching for planets around other stars, one of the surprising discoveries was that there are planets orbiting white dwarfs. The first exoplanets we ever discovered were white dwarf planets. Of course, these planets were barren and stripped of any atmosphere, so we had to look at main sequence stars to find potentially habitable worlds. Or so we thought.
As we discovered more white dwarf planets, it became clear that some of them might retain atmospheres and water. Perhaps they were an outer planet with a thick atmosphere before their star swelled to a red giant, or perhaps some of the gas ejected by the star to become a white dwarf was captured by the world. Regardless of the method, a small percentage of white dwarf planets retain an atmosphere. But to be habitable, they would need to migrate inward to the white dwarf in order to enter the habitable zone. We knew that planets could migrate during the red giant stage of their star, but it wasn’t until recently that computer simulations showed they could move close enough and remain in stable orbits within the potentially habitable zone of a white dwarf. So we now know that while the odds are long, it is possible for white dwarf stars with water-rich atmospheres to exist.
But there’s one other problem. White dwarfs don’t have nuclear engines in their cores. They can’t continue to generate heat for billions of years, but rather cool down gradually over time. This means that on a cosmic scale, their habitable zone shrinks and moves inward over time. Any planet in the center of the zone would soon find itself on the outer edge of the zone and eventually in the cold, inhospitable beyond. But a new study contradicts this idea, at least for some white dwarfs.
Habitable zone for a paused white dwarf. Credit: Vanderburg, et al
The study notes that about 6% of white dwarfs seem to pause their rate of cooling. This is likely due to a process known as distillation. Although the core of a white dwarf doesn’t undergo fusion, there are still processes such as radioactive decay and other nuclear interactions. As neutron-rich isotopes such as neon-22 distill, the interior of the white dwarf shifts, releasing a great deal of gravitational energy. This continues to heat the star, allowing it to maintain its temperature.
The team found that this distillation process can pause the cooling of a white dwarf for 10 billion years, meaning that the habitable zone of the white dwarf would be stable for that time. That’s roughly the same timespan as the lifetime of the Sun, so there would be plenty of time for life to evolve and thrive. This only occurs in a fraction of white dwarfs, but it means that our search for life on white dwarf stars should focus on those with paused cooling.
In the more than sixty years where scientists have engaged in the Search for Extraterrestrial Intelligence (SETI), several potential examples of technological activity (“technosignatures”) have been considered. While most SETI surveys to date have focused on potential radio signals from distant sources, scientists have expanded the search to include other possible examples. This includes other forms of communication (directed energy, neutrinos, gravitational waves, etc.) and examples of megastructures (Dyson Spheres, Clarke Bands, Niven Rings, etc.)
Examples of modern searches include Project Hephaistos, the first Swedish Project dedicated to SETI. Named in honor of the Greek god of blacksmiths, this Project is focused on the search for technosignatures in general rather than looking for signals deliberately sent toward Earth. In a recent paper, a team led by the University of Manchester examined a Dyson Sphere candidate identified by Hephaistos. Their results confirmed that at least some of these radio sources are contaminated by a background Active Galactic Nucleus (AGN).
The team was led by Tongtian Ren, a Ph.D. student in astrophysics from the Jodrell Bank Centre for Astrophysics at the University of Manchester. He was joined by Prof. Michael Garrett, his supervisor at the University of Manchester, the Leiden Observatory, and the Institute of Space Sciences and Astronomy at the University of Malta; and Andrew Siemion, an Associate Research Astronomer at the Berkeley SETI Research Center, the SETI Institute, and the University of Oxford. The paper that describes their findings recently appeared in the Monthly Notices of the Royal Astronomical Society.
Dyson Spheres are a class of megastructures originally proposed by physicist Freemon Dyson, who proposed how advanced civilizations could create structures large enough to enclose their stars (thus harnessing all of their energy). Project Hephaestos, led by Prof. Erik Zackrisson, has published numerous papers exploring possible Dyson Sphere candidates using different methods and data sources. The fourth and most recent paper in the series focused on seven potential candidates (designated A to G) around M-type stars from a sample of 5 million detected by the ESA’s Gaia Observatory.
Previously, Ren and his team have investigated these candidates to identify possible natural explanations. As they explored in a previous paper, these include dust-rich debris disks that absorb light and re-emit it as infrared radiation. This will lead to an observed infrared excess, which Dyson proposed as a possible indication of his proposed megastructure. However, as they indicate in their most recent paper, the Project’s measurements do not appear to resemble typical debris disks. As Garrett explained to Universe Today via email:
“When I saw the original results from Project Hephaestos last year, I was skeptical – they had surveyed 5 million stars, and if you do that, there is a good chance your measurements might include emission from background sources. You don’t expect stars to show radio emission at this level, and it basically tells you that the radio emission is probably coming from background (radio) galaxies. But then you also need a special kind of galaxy that is faint in the optical but very bright in the infrared – the only galaxies I knew that had this characteristic are DOGs – Dust Obscured Galaxies.”
The team was also inspired by another paper by Jason T. Wright, a professor of astronomy and astrophysics at Penn State, the director of the Penn State Extraterrestrial Intelligence Center (PSETI), and a member of the Center for Exoplanets and Habitable Worlds (CEHW). In this paper, Wright hypothesized that a true Dyson Sphere might use radio emissions to discharge waste heat. This led them to consider the possibility that these candidates were indeed Dyson Spheres.
Artist’s impression of a bright, very early active galactic nucleus. Credit: NSF/AUI/NSF NRAO/B. Saxton
As Tongtian explained, they were also inspired by previous research by Garrett:
“Mike briefly argued in 2015 that even in a Kardashev Type I Civilization, where energy consumption is significantly higher than that of humans on Earth, their radio communication signals are too weak to detect. However, the Dyson Spheres could correspond to a Kardashev Type II Civilization—one that harnesses over a billion times more energy than a Type I Civilization. Therefore, regardless of whether the beings reside on planets or elsewhere near the Dyson Sphere, it might be possible to detect their use of similar electromagnetic technologies.”
To investigate these possibilities further, the team searched through data obtained by the enhanced Multi-Element Radio Linked Interferometer Network (e-MERLIN) and the European VLBI Network (EVN) for data on the brightest radio source (candidate G). To their surprise, they found that three candidates from Project Hephaestos had radio counterparts in the astronomy databases. As Tongtian explained, the most logical explanation is that these signals (including candidate G) were due to contamination from bright radio sources – Active Galactic Nuclei (AGN) – in the background:
“They shouldn’t belong to one civilization. Otherwise, many anomalous stars would be connected as a swarm in the sky, not isolated seven. At that moment, we realized that either different extraterrestrial civilizations located hundreds of light-years away all have mastered the same or similar advanced radio emission technologies, or these signals originate from some form of natural contamination. We preferred to assume that they were some natural objects beyond the Milky Way – and most likely to be hot DOGS.”
These results effectively confirmed their earlier hypothesis that at least some of the candidates identified by Project Hephaistos are contaminated by bright radio sources that are also very bright in the infrared wavelength. This causes them to mimic the characteristics that Freeman Dyson predicted and what astronomers expect from Dyson Spheres. However, this does not rule out the remaining six candidates and highlights the importance of thoroughly analyzing each candidate with high-resolution radio observations.
Artist’s impression of a Dyson Sphere, a megastructure associated with a Type II Civilization. Credit: SentientDevelopments.com
“We don’t know that all of the candidates are contaminated, but some, maybe all, probably are. I really hope some of them are indeed good Dyson Sphere candidates,” said Garrett. “This all shows that a multiwavelength approach is really required when looking for candidates in order to rule out background contamination.”
“The development of new astronomical instruments does not follow the rapid update cycles of consumer electronics—it takes decades,” added Tongtian. “Gaia (launched in 2013 and recently decommissioned) and WISE (launched in 2009 and expired in 2024) provided a crucial observational window. The next generation of similar probes may not be available for a long time, making it unlikely that a large-scale Dyson Sphere search program like Project Hephaistos will be conducted again in the near future. So the current seven Dyson Sphere candidates deserve to be carefully examined.”
