Within the greater than sixty years the place scientists have engaged within the Search for Extraterrestrial Intelligence (SETI), a number of potential examples of technological exercise (“technosignatures”) have been thought of. Whereas most SETI surveys thus far have centered on potential radio alerts from distant sources, scientists have expanded the search to incorporate different potential examples. This consists of different types of communication (directed power, neutrinos, gravitational waves, and so on.) and examples of megastructures (Dyson Spheres, Clarke Bands, Niven Rings, and so on.)
Examples of contemporary searches embody Project Hephaistos, the primary Swedish Undertaking devoted to SETI. Named in honor of the Greek god of blacksmiths, this Undertaking is targeted on the seek for technosignatures typically reasonably than in search of alerts intentionally despatched towards Earth. In a recent paper, a staff led by the College of Manchester examined a Dyson Sphere candidate recognized by Hephaistos. Their outcomes confirmed that at the very least a few of these radio sources are contaminated by a background Energetic Galactic Nucleus (AGN).
The staff was led by Tongtian Ren, a Ph.D. pupil in astrophysics from the Jodrell Bank Centre for Astrophysics on the College of Manchester. He was joined by Prof. Michael Garrett, his supervisor on the College of Manchester, the Leiden Observatory, and the Institute of Space Sciences and Astronomy on the College of Malta; and Andrew Siemion, an Affiliate Analysis Astronomer on the Berkeley SETI Analysis Middle, the SETI Institute, and the College of Oxford. The paper that describes their findings just lately appeared within the Monthly Notices of the Royal Astronomical Society.
Dyson Spheres are a category of megastructures initially proposed by physicist Freemon Dyson, who proposed how superior civilizations might create buildings giant sufficient to surround their stars (thus harnessing all of their power). Undertaking Hephaestos, led by Prof. Erik Zackrisson, has printed quite a few papers exploring potential Dyson Sphere candidates utilizing totally different strategies and information sources. The fourth and most up-to-date paper within the sequence centered on seven potential candidates (designated A to G) round M-type stars from a pattern of 5 million detected by the ESA’s Gaia Observatory.
Beforehand, Ren and his staff have investigated these candidates to determine potential pure explanations. As they explored in a earlier paper, these embody dust-rich particles disks that take in mild and re-emit it as infrared radiation. This can result in an noticed infrared extra, which Dyson proposed as a potential indication of his proposed megastructure. Nevertheless, as they point out of their most up-to-date paper, the Undertaking’s measurements don’t seem to resemble typical particles disks. As Garrett defined to Universe Immediately by way of electronic mail:
“After I noticed the unique outcomes from Undertaking Hephaestos final 12 months, I used to be skeptical – that they had surveyed 5 million stars, and in the event you do this, there’s a good probability your measurements may embody emission from background sources. You don’t count on stars to indicate radio emission at this stage, and it mainly tells you that the radio emission might be coming from background (radio) galaxies. However you then additionally want a particular form of galaxy that’s faint within the optical however very brilliant within the infrared – the one galaxies I knew that had this attribute are DOGs – Mud Obscured Galaxies.”
The staff was additionally impressed by one other 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 may use radio emissions to discharge waste warmth. This led them to contemplate the likelihood that these candidates had been certainly Dyson Spheres.
As Tongtian defined, they had been additionally impressed by earlier analysis by Garrett:
“Mike briefly argued in 2015 that even in a Kardashev Sort I Civilization, the place power consumption is considerably greater than that of people on Earth, their radio communication alerts are too weak to detect. Nevertheless, the Dyson Spheres might correspond to a Kardashev Sort II Civilization—one which harnesses over a billion instances extra power than a Sort I Civilization. Due to this fact, no matter whether or not the beings reside on planets or elsewhere close to the Dyson Sphere, it may be potential to detect their use of comparable electromagnetic applied sciences.”
To research these prospects additional, the staff searched by way of information obtained by the enhanced Multi-Element Radio Linked Interferometer Network (e-MERLIN) and the European VLBI Network (EVN) for information on the brightest radio supply (candidate G). To their shock, they discovered that three candidates from Undertaking Hephaestos had radio counterparts within the astronomy databases. As Tongtian defined, probably the most logical clarification is that these alerts (together with candidate G) had been as a consequence of contamination from brilliant radio sources – Energetic Galactic Nuclei (AGN) – within the background:
“They shouldn’t belong to at least one civilization. In any other case, many anomalous stars could be linked as a swarm within the sky, not remoted seven. At that second, we realized that both totally different extraterrestrial civilizations situated a whole bunch of light-years away all have mastered the identical or comparable superior radio emission applied sciences, or these alerts originate from some type of pure contamination. We most popular to imagine that they had been some pure objects past the Milky Approach – and most definitely to be scorching DOGS.”
These outcomes successfully confirmed their earlier speculation that at the very least a few of the candidates recognized by Undertaking Hephaistos are contaminated by brilliant radio sources which can be additionally very brilliant within the infrared wavelength. This causes them to imitate the traits that Freeman Dyson predicted and what astronomers count on from Dyson Spheres. Nevertheless, this doesn’t rule out the remaining six candidates and highlights the significance of totally analyzing every candidate with high-resolution radio observations.
“We don’t know that all the candidates are contaminated, however some, perhaps all, in all probability are. I actually hope a few of them are certainly good Dyson Sphere candidates,” mentioned Garrett. “This all reveals {that a} multiwavelength method is admittedly required when in search of candidates with a view to rule out background contamination.”
“The event of recent astronomical devices doesn’t comply with the fast replace cycles of client electronics—it takes many years,” added Tongtian. “Gaia (launched in 2013 and just lately decommissioned) and WISE (launched in 2009 and expired in 2024) offered an important observational window. The subsequent era of comparable probes is probably not out there for a very long time, making it unlikely {that a} large-scale Dyson Sphere search program like Undertaking Hephaistos will probably be performed once more within the close to future. So the present seven Dyson Sphere candidates should be rigorously examined.”
