A recent SETI (Search for Extraterrestrial Intelligence) effort focused on a famous supernova from 1987, working under the premise that aliens might use such events to draw attention to themselves with synchronized beacons. Although this hunt came up short, it lays the groundwork for future searches using the same innovative strategy.
This principle, called the SETI Ellipsoid strategy, offers a potential solution to a challenging problem: How do you coordinate efforts with someone when you’re unable to communicate? This applies whether it’s in the search for undiscovered alien civilizations or connecting with a friend on Earth.
Seems hopeless, but U.S. economist and game theorist Thomas Schelling popularized a kind of solution, now known as Schelling points, to this problem in his book The Strategy of Conflict. Sure, two unconnected people who want to meet can’t directly coordinate their efforts, but they can still use their brains.
For example, if I became separated from my wife at an amusement park, and my phone died, I wouldn’t just give up on trying to reconnect. I’d use rational thinking, social norms, and an understanding of my wife’s tendencies to find her, while simultaneously operating on the premise that she’s employing a similar thought process. So, I’d make my way to the entrance in hopes that she followed suit, or failing that I’d go to our car in the parking lot. Here, the entrance and the car serve as Schelling points.
Here’s an example from the U.S. Navy: Two Americans at random locations wanting to locate each other might independently choose New Year’s Eve as a logical date for meeting, New York as the most probable city, and a popular location, such as under the clock at Grand Central Station or somewhere near the ball in Times Square. Obviously, a proposed Schelling Point is no guarantee of success, but it helps in situations in which information or communication is extremely limited.
Such is the state of being for SETI researchers, many of whom work under the assumption that alien civilizations are trying to reach out to us. The challenge is knowing where to look. But as the Schelling concept reminds us, we should employ our brains and actively search for obvious ways in which an undetected alien civilization, despite being far, far away, might be capable of communicating with us, knowing that we thought similarly about a Schelling point.
In the case of SETI, potential Schelling points should be something rare, blatantly obvious, detectable across vast cosmic distances, and of great interest. Thankfully, such a thing exists: supernovae. This idea dates back to the 1990s, when SETI scientist Guillermo Lemarchan proposed that intelligent extraterrestrials might utilize supernovae—massive stellar explosions signaling the final phase of a star’s life—as focal points for establishing Schelling points. Lemarchan even proposed a specific supernova: SN 1987A. This colossal supernova, detected 37 years ago, resides just 168,000 light years from Earth in our galactic sidekick, the Large Magellanic Cloud.
Inspired by this research, and in possession of the data required to perform such a survey, a research team from the SETI Institute, Berkeley SETI Research Center, and the University of Washington sought to detect an optical alien beacon, or technosignature, emanating from a SETI Ellipsoid located between SN 1987A and Earth. And they did so using data gathered from NASA’s ongoing Transiting Exoplanet Survey Satellite (TESS) mission. Sounds complicated, but the SETI Ellipsoid is easy to grok once you break it down.
The first thing that has to happen is the supernova itself, which is eventually detected by an alien civilization. Alerted to the supernova and acting almost immediately, the alien civilization broadcasts a powerful beacon in the hopes of attracting the attention of an unknown civilization. The basic idea is that the unknown civilization, like our very own, would naturally look in the general direction of the supernova in hopes of studying the rare celestial event.
But because aliens (presumably) have brains and because they assume that we have brains, they would also recognize this as an opportunity to utilize the Schelling principle, in that both parties, though unaware of each other, mutually recognize the supernova as an opportunity to find one another. Needless to say, the beacon would have to bear features of artificiality, i.e. something not possibly caused naturally and something only alien civilizations would transmit, for astronomers on Earth to clock it as an anomaly.
As for the ellipsoid itself, it represents the growing space in which the supernova is theoretically visible by both the alien civilization and Earth. From our perspective on Earth, we should therefore search for the alien civilization within this ellipsoid. Or as the scientists write in their study, published in the Astronomical Journal, the SETI Ellipsoid “helps select outliers or signals that are interesting and require further analysis or follow-up from a technosignature standpoint.” An animated graphic (above) prepared by the SETI Institute encapsulates this concept quite adeptly.
As noted, the researchers used TESS data for their recent scan. “New surveys of the sky provide groundbreaking opportunities to search for technosignatures coordinated with supernovae,” said co-author Bárbara Cabrales, a scientist from the SETI Institute and the Berkeley SETI Research Center at the University of California, Berkeley, said in a press release.
It’s important to keep in mind, of course, that we’re talking about immense timescales, given the time it takes a signal to reach a given location. As noted, SN 1987A is 168,000 light-years away, so any potential alien signal is likely to have originated thousands upon thousands of years ago.
The team analyzed data over a one-year period “to cover our bases,” Cabrales said, using 3D location data from Gaia Early Data Release 3 (which concluded in 2017), and identified 32 prime targets within the southern TESS continuous viewing zone associated with the SETI Ellipsoid. Looking intently at these targets, the scientists sought to discern normal behavior from potential technosignatures. Sadly, this initial scan revealed no anomalies, but this initiative now sets the stage for similar, more exhaustive efforts.
“This is a great demonstration of how we can prioritize our search efforts by considering what sorts of synchronization schemes other species might employ to get our attention,” explained Jason Wright, professor of astronomy and astrophysics at Penn State Extraterrestrial Intelligence Center, in an email to Gizmodo. “It’s a big sky, and anything we can do to narrow down our search space can only help the search for extraterrestrial technological species,” said Wright, who wasn’t involved in the research.
Indeed, the recent study marks a good starting point, guiding SETI researchers to explore large archival databases. They should conduct searches with a wider range of targets and diverse signal types, expanding the scope of astronomical research and building on current findings.
What’s more, the paper should be of interest to METI-minded researchers, that is, Messages to Extraterrestrial Intelligences. Should a supernova happen nearby in the coming years, we could use the opportunity to transmit a beacon alerting others to our presence. As to whether we should do that, that’s another story.
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