Variable stars might be the answer to our search for extraterrestrials

Humanity’s intrigue lies in the pursuit of extraterrestrial existence. Utilizing telescopes and spacecraft, we scrutinize faraway planets for indications of habitable conditions. Employing advanced technologies and radio signals, we endeavor to detect potential cosmic counterparts. This ongoing exploration, fueled by curiosity and the thirst for revelation, progressively broadens our cosmic outlook.

For nearly ten years, the Gaia Observatory from the European Space Agency has maintained a steadfast presence at the Earth-Sun L2 Lagrange Point. As an astrometry endeavor, Gaia embarks on collecting information regarding the locations, motion, and speed of stars, exoplanets, and entities within the Milky Way and numerous nearby galaxies. As its primary mission concludes by 2025, Gaia is set to have surveyed around 1 billion celestial objects, culminating in the formulation of an unparalleled, supremely precise 3D space catalog.

How can variable stars help us find extraterrestrials?

The European Space Agency (ESA) has carried out three data releases stemming from the Gaia mission, with the most recent (DR3) unveiled in June 2022. Beyond the groundbreaking insights these unveilings have provided, scientists are uncovering novel utilities for this astrometric data. In a recent investigation, a group of astronomers proposed that Gaia Data Release 3’s compilation of variable stars might aid the Search for Extraterrestrial Intelligence (SETI). By aligning the hunt for transmissions with noteworthy occurrences such as supernovae, scientists could refine their quest for extraterrestrial signals.

Helmed by Andy Nilipour, an undergraduate scholar within the Yale University Department of Astronomy, the research assembled a team. This included James R.A. Davenport, a Research Scientist at the University of Washington, Seattle; Steve Croft, an Adjunct Senior Astronomer affiliated with the Radio Astronomy Lab and the SETI Institute at UC Berkeley; and Andrew Siemion, who holds the Bernard M. Oliver Chair for SETI Qualification at UC Berkeley, alongside connections to the Jodrell Bank Centre for Astrophysics (JBCA) at the University of Manchester and the Institute of Space Sciences and Astronomy at the University of Malta.

Featured in The Astronomical Journal under the title “Signal Synchronization Strategies and Time Domain SETI with Gaia DR3,” this research marked Nilipour’s inaugural academic investigation. Nilipour shared, in an interaction with Yale News, that his mentors, Steve Croft, and James Davenport, deliberately selected this avenue for him. The aim was to formulate a geometric methodology to delimit technosignature searches, a task he acknowledged as one of the foremost challenges in the field of SETI. This complexity arises from the multitude of potential transmission origins and signal characteristics.

Technosignatures can indicate extraterrestrial life

In straightforward terms, technosignatures serve as indications of an advanced technological society’s activity. Historically, SETI endeavors predominantly focused on seeking radio signals due to their proven feasibility and effective space propagation. Notably, Breakthrough Listen stands out as an exemplary and thorough initiative in this realm. These pursuits encompassed the practice of tuning into diverse stars over defined durations, anticipating the detection of radio signals originating from orbiting planets. Yet, in recent times, researchers have broadened the scope of potential technosignatures, exploring alternative avenues. 

In their investigation, Nilipour and his team theorized that an advanced civilization would comprehend the formidable challenge of monitoring all spatial dimensions around their planet in every potential mode, encompassing radio, optical, infrared, ultraviolet, x-ray, and gamma-ray, among others. 

Consequently, they might strategically time their signals of potential communication (optimistically!) to coincide with notable astrophysical occurrences that could captivate observers’ attention – such as supernovae. Nilipour initiated the development of this theory during a summer undergraduate program facilitated by the National Science Foundation (NSF) and the Breakthrough Listen Initiative at the Berkeley SETI Research Center.

How will this approach trace technosignatures?

Commencing their endeavor, Nilipour and his collaborators initiated with an initial stride. They handpicked four supernovae from the annals of history spanning the last millennium and meticulously scrutinized the duration it took for the luminous aftermath of these explosions to traverse space and finally grace Earth.

Upon analysis, they deduced that the luminous aftermath generated by these four occurrences necessitated durations of 6,300 years, 8,970 years, 16,600 years, and 168,000 years to finally grace Earth. Subsequently, they conducted a comparative assessment by juxtaposing these findings with light signals from a vast assemblage of over 10 million stars, meticulously documented by the Gaia observatory and encompassed within the DR3 catalog. 

This scrutiny unveiled a revelation: among these stellar sources, 465 emitted light that arrived on Earth over the same time spans as the supernovae, while 403 stars emitted light signals from an advantageous perspective in relation to these explosive events. Despite the absence of technosignatures within the 868 systems scrutinized, their outcomes have nonetheless supplied valuable parameters to inform future investigations. 

As Nilipour pointed out, their approach is adaptable for exploring additional archival data, and uncovering potential traces of technosignatures:

“Finding a technosignature would have been incredible, but this really was more about showing a methodology that we can use in the future. What we’ve done here can be applied to additional Gaia data, to data from TESS [the Transiting Exoplanet Survey Satellite], and to other data as it becomes available. We’re currently running the same type of analysis using a new supernova in the galaxy M101 that became visible in May of this year, which is the closest supernova in over a decade.”

Do we have the time and resources for such observations?

Considering the vast multitude of stars within our galaxy, the inherent backdrop of cosmic commotion, the urgency linked to deciphering transmissions, and the added complexity of plausible false positives, embarking on a hunt for prospective technosignatures presents a highly formidable challenge. 

Achieving comprehensive, continuous surveillance of every celestial sector in a range of wavelengths would be ideal, eventually enabling the detection of signals (if they were being emitted). However, this exhaustive all-sky observation remains unattainable due to constraints of time and resources.

This is where the significance of studies like these shines: they methodically refine the search scope by investigating diverse technosignature variations, frequency spans, and celestial positions. Gradually, SETI scientists enhance the likelihood of unequivocal detections that can be verified through subsequent inquiries. Amid the vast cosmic expanse and numerous potentials, if there’s a needle to uncover in this celestial haystack, its revelation is only a matter of time.