Firefly-Inspired Model Seeks Alien Signals That Stand Out From Pulsars, Study Says

Searches for extraterrestrial intelligence mostly look for the familiar: radio signals like the ones humans have been emitting for a hundred years. A group of American researchers argues that approach could miss the mark, and they have borrowed an idea from fireflies to propose another way to think about what an alien broadcast might look like.

Writing in the journal Scientific Reports, the scientists, from universities in the southwestern United States, say "new paradigmatic frameworks could be necessary to recognize intelligent alien signals in astronomical data." One reason is that Earth is becoming less "radio loud" as it moves to cable TV and the internet, and any civilization out there might have had a similarly brief period of radio activity. Since 2016, the Breakthrough Listen initiative has also looked for optical laser transmissions.

The team, whose lead author is Cameron Brooks of Arizona State University, noted work like the Earth Species Project, where researchers use machine learning to study animal communication. They then built a toy model, a simplified representation of a complex system meant to capture only its essential features, of how detectable a signal is. The model was inspired by fireflies.

In mating season, fireflies produce sequences of flashes, usually at twilight, through bioluminescence from a light-emitting organ on the abdomen. Flying males reveal themselves to females on the ground. The patterns vary in the length of each flash, timing, color, number and rate of repetitions, height and direction of flight, and they differ by species and by region.

The researchers used a 2022 paper by Chantal Nguyen and colleagues, which examined how firefly mating signals might co-evolve in the visual chaos of a swarm while staying distinct from other species and conserving energy. Flashing costs a firefly energy and exposes it to predators. Applying the same logic, Brooks and colleagues evolved an alien signal that is "maximally distinct from a background of highly ordered, naturally occurring signals generated by pulsars, while also minimizing energy consumption."

Pulsars are highly magnetized, rapidly spinning neutron stars that sweep a bright, regular beam across space. An estimated 100,000 exist in the Milky Way, and we can detect one when its beam crosses the plane of Earth's orbit. When pulsars were first discovered in 1967, their behavior was so odd that some speculated they were broadcasts from extraterrestrials. Any intelligent aliens trying to announce themselves with a pulsed radio beam would presumably want to look different from the pulsars nearby.

The model is not meant to search for literal firefly-like flashes. It works with more abstract features of a signal pattern, such as the repetition period and the pulse duration, and asks which combinations are easiest to tell apart from the natural pulsar background. It remains a toy model and has not detected anything. Its value is as a framework for deciding what kinds of patterns deserve a second look in telescope data.