Technosignatures Around White Dwarfs, Massive Stars, and Stellar Bycatch
Three poster presentations from IAU Symposium 404 explore overlooked technosignature targets, stellar radio foregrounds, and a smarter way to count the stars we've already surveyed.
What makes a good target for the search for technosignatures?
The obvious answers like nearby Sun-like stars, planets in the classical Goldilocks zone, and the galactic neighborhood we know best have dominated the field for decades. But three poster presentations from IAU Symposium 404: Advancing the Search for Technosignatures push in different directions. One makes the case that stellar remnants called white dwarfs deserve far more attention than they’ve received. Another reminds us that before we can hear faint planetary signals in the radio, we need to understand the loud, stormy environments that surround massive stars. And a third asks a more statistical question: of all the stars a radio telescope has already swept past without meaning to, how many have we actually counted, and what might those numbers tell us about the rarity of technological civilizations?
Together, these three short presentations reflect something important about the current moment in technosignature science: the field is maturing, and the questions are getting sharper.
The White Dwarf Technosignature Opportunity
Caldon T. Whyte & Colin Harrison — Florida Institute of Technology
When people imagine the search for extraterrestrial civilization, they tend to picture Sun-like stars: stable, warm, familiar. But Caldon Whyte and Colin Harrison argue that a very different kind of stellar object—the white dwarf—deserves a prominent place in technosignature surveys, and they offer several converging reasons why.
White dwarfs are what most stars in the galaxy, including our own Sun, eventually become. After exhausting their nuclear fuel, stars like the Sun swell into red giants before shedding their outer layers and leaving behind a dense, Earth-sized remnant that slowly cools over billions of years. They are, in short, the most common final destination in stellar evolution. And that commonality matters: if we want to know whether the galaxy has produced other technological civilizations, these are the objects most of those civilizations’ host stars eventually become.
The habitability case for white dwarfs is not new. Previous modeling work has shown that white dwarfs could sustain both photosynthesis and ultraviolet-driven abiogenesis in the Goldilocks zones of orbiting planets: meaning that, in principle, enough energy could reach a planetary surface to support life and possibly even its origin. Whyte’s prior published research demonstrated this with a model calibrated to real astrophysical parameters. But his IAUS404 presentation extends that foundation into explicitly technosignature territory.
The poster identifies several distinct mechanisms that could produce detectable technosignatures around white dwarfs. First, there is the transmission spectroscopy advantage: white dwarfs are small, meaning that an orbiting planet transiting in front of one creates a proportionally large signal. Atmospheric features would produce much stronger spectroscopic signatures than they would around a larger star, making white dwarfs unusually favorable targets for instruments like JWST. Second, any civilization that originated around a Sun-like star would eventually face a crisis as that star expanded toward the red giant phase; a cataclysm that would either destroy their world or drive them to migrate, engineer solutions, or seek new homes. Either scenario could leave behind distinctive signatures. Third, advanced civilizations may have actively sought out white dwarfs for their stable, long-lived environments: a slowly cooling remnant provides billions of years of relatively quiet conditions, which might be exactly what a civilization with long time horizons would want.
Taken together, Whyte and Harrison argue that these converging possibilities make white dwarfs high-value targets that have been systematically underweighted in the survey planning to date.
You can view the full poster here.
Low-Frequency Radio Emission from Massive Stars as a Precursor for Exoplanet Radio Searches
Daniel Kanev, Joe Callingham, & Jasmina Lazendic-Galloway — Eindhoven University of Technology
One of the most exciting frontiers in exoplanet science is the possibility of detecting radio emission directly from planets, specifically the kind of coherent, low-frequency auroral emission that planets with strong magnetic fields produce when those fields interact with stellar winds. Earth’s own magnetosphere generates this kind of emission; Jupiter produces it in abundance. If we could detect similar signals from planets around other stars, we would have a direct probe of their magnetic fields, their space weather environments, and potentially their habitability.
The technical challenge is significant. Exoplanetary radio signals, if they exist at detectable levels, are faint, and they exist against a background of much brighter astrophysical noise. That noise comes in part from the stellar environments themselves. Before a radio telescope can confidently attribute a signal to a planet, it needs a detailed understanding of what the host star and its surrounding medium are doing at the same frequencies.
Daniel Kanev and his collaborators take a step back from the planet-detection question itself to address this prerequisite: characterizing the low-frequency radio environments of massive stellar systems. Massive stars (the kinds that are hot, luminous, and energetically active) drive powerful stellar winds and produce strong magnetic fields that accelerate particles and generate non-thermal radio emission through shock interactions. Understanding the low-frequency radio behavior of stellar systems is important not only for what those emissions reveal about the stars themselves, but because stellar activity has a direct influence on planetary habitability and because stellar noise must be characterized before faint planetary signals can be extracted.
In this observational study, Kanev and his team present their analysis of low-frequency radio emission from massive stellar systems, building the kind of empirical characterization that future exoplanet radio searches will depend on. The work is explicitly framed as preparatory: a foundation for the detection campaigns that next-generation facilities like the Square Kilometre Array will eventually undertake. It reflects a growing recognition in the field that the path to hearing planets first runs through a thorough accounting of their stellar neighborhoods.
Simulating the Stellar Bycatch: Constraining the Prevalence of Extraterrestrial Transmitters within Radio SETI Surveys
Louisa Mason, Michael A. Garrett, & Andrew P.V. Siemion — University of Manchester
When a radio telescope points at a star to search for technosignatures, it does not see only that star. The telescope’s field of view is a cone that extends through the galaxy, and within that cone of space lies many more stars at greater distances. These incidental targets are what Mason, Garrett, and Siemion call the “stellar bycatch”: the stars a survey captures without intending to.
Previous work, including efforts that used ESA’s Gaia spacecraft to catalog stars within survey fields, has begun accounting for bycatch to refine estimates of how common radio-transmitting civilizations could be. But Gaia remains limited by magnitude cutoffs, astrometric uncertainties at large distances, and confusion in crowded regions of the sky, meaning that Gaia-based bycatch estimates represent a lower bound on the true stellar populations within those fields.
To address this, Mason and her collaborators turn to the Besançon Galactic Model, a sophisticated computational tool that simulates the statistical structure of the Milky Way’s stellar population along any line of sight, including stars too faint, too distant, or too confused for Gaia to resolve cleanly. Applying this approach to the Breakthrough Listen Enriquez/Price survey, the team modeled more than six million stellar objects across 1,229 individual telescope pointings, extending the reach of the analysis out to 25 kiloparsecs—well into the far reaches of the galaxy.
The result is tighter and more realistic constraints on transmitter prevalence. The analysis suggests that no more than roughly 0.001% of stellar systems within 2.5 kiloparsecs are home to high-duty-cycle radio transmitters detectable at the sensitivity levels of the Enriquez/Price survey. Just as importantly, the work offers a reframing of how we think about SETI survey bias: the team concludes that radio surveys are, in fact, far less anthropocentrically constrained than commonly assumed, because the bycatch passively includes a much broader diversity of stellar types than the nominal target list would suggest.
Mason has also made the team’s Besançon-based simulator publicly available on GitHub, extending the tool’s usefulness to the broader research community.
Read more about this work on arXiv.
Key Takeaways from These IAUS404 Posters
White dwarfs offer compounding advantages as technosignature targets: their small size makes transmission spectroscopy more sensitive, civilizations facing stellar evolution may have left unique signatures nearby, and long-term galactic habitability considerations may have drawn advanced intelligence to these systems.
Stellar environments must be characterized before planets can be heard: Kanev et al.’s work on massive-star radio emission is foundational infrastructure for the next era of exoplanet radio searches, not a detour from it.
Radio surveys reach far deeper than their target lists suggest: the “stellar bycatch” of unintended background stars dramatically expands the population surveyed in any radio SETI campaign, and accounting for it yields both tighter transmitter prevalence limits and a less anthropocentric picture of what we’ve actually searched.
The question of where to look is inseparable from the question of how to count what we’ve already looked at: all three presentations, in different ways, are about refining the search geometry: expanding it in the case of white dwarfs, clarifying it in the case of stellar foregrounds, and more accurately mapping it in the case of bycatch statistics.
Early-career researchers are driving methodological innovation: Whyte, Kanev, and Mason are all graduate students leading work that connects directly to the observational priorities of facilities like JWST, LOFAR, and the SKA.
Technosignature science has always had to wrestle with a particular kind of uncertainty: we don’t know what we’re looking for well enough to be sure we’d recognize it, and we don’t know where to look well enough to be confident our surveys are covering the right ground. The three presentations gathered here highlight how researchers are honing their craft in technosignature science to better understand the uncertainties so we can expand our searches and our knowledge.
Whyte and Harrison show that the most common stellar endpoints in the galaxy have been largely ignored as targets, and make a credible case for why that should change. Kanev and colleagues remind us that hearing a planet in the radio requires first understanding the noise it’s embedded in. And Mason, Garrett, and Siemion demonstrate that even surveys we’ve already run have been reaching further and covering more stellar diversity than we realized. In combination, they point toward a search that is becoming more rigorous, more self-aware, and more willing to look in the places it has not yet thought to look.
These presentations were delivered as part of IAU Symposium 404: Advancing the Search for Technosignatures, hosted jointly by the International Astronomical Union and the Blue Marble Space Institute of Science, 2–6 March 2026.
Thanks for joining us here with Planetary Perspectives, an editorial endeavor and science communication project from Blue Marble Space.
