For more than 60 years, scientists have been listening for signals from aliens. But space is vast. No one knows for sure where to point the antennas in order to have the best chance of capturing an extraterrestrial broadcast—a “technosignature.”
A team led by James Davenport, a University of Washington astronomer who focuses on the search for extraterrestrial intelligence (SETI), has an idea. Riffing on a new concept called a “SETI ellipsoid,” Davenport and his team have pointed two radio telescopes—the Allen Telescope Array in California and the Green Bank Telescope in West Virginia—at a recently detected supernova originating in the M101 galaxy, 21 million light-years away from Earth.
That supernova, named SN 2023ixf, is the result of the collapse and subsequent explosion of a supermassive star. It’s the first of its type that scientists have detected in a decade.
Astronomically speaking, it’s a big deal. Davenport and his team are betting that if aliens exist and practice astronomy the way we do, they’ve also detected the exploding star—and also appreciate its scientific significance. If that’s the case, the aliens might reasonably assume that any other technological civilizations out there in the cosmos are paying close attention to SN 2023ixf. After all, we are.
If the aliens want to be heard, they might time a powerful broadcast—a welcome message, in essence—so that, in an ellipsoid-shaped region of space, the signal overlaps with the electromagnetic energy radiating from the supernova. Other civilizations should already be pointing their antennas in the direction of SN 2023ixf. So they should detect the welcome message, too.
“In this framework, extraterrestrial agents would use noteworthy events such as galactic novae or supernovae to coordinate signal transmission,” Davenport and his team wrote in a recent follow-up notice to their peer-reviewed article that appeared in The Astronomical Journal in September. “This approach provides an elegant solution for when and where to search for technosignatures.”
“The ellipsoid idea definitely assumes that there are astronomers on both ends, that someone like us would notice a supernova and think to be observing near it,” Davenport told The Daily Beast.
The SETI ellipsoid idea hinges on some other assumptions. First, that aliens might exist. Second, that they do astronomy like we do: with powerful instruments including radio telescopes. And finally, that these beings might be a technologically advanced civilization on one of the rocky planets orbiting that yellow dwarf star in what we call the Orion Arm of the Milky Way galaxy—and have timed a signal to reach us at the same time the energy from the supernova does.
The first assumption is a prerequisite to SETI and related fields of science. And the second assumption is reasonable, Ross Davis, a specialist in information and communication sciences at Indiana University, told The Daily Beast. “It can be a safe assumption as long as it’s not interpreted to extremes.”
One extreme said Davis, would be to “over-anthropomorphize” possible aliens by assigning them too many human qualities like curiosity about the universe—and a desire to communicate with other intelligent beings. The other extreme risks “under-anthropomorphizing” aliens by imagining them as completely different from us. We all live in the same universe and are subject to the same laws of physics and biology that shape our evolution. Why wouldn’t two different intelligent species be equally curious—and equally eager to make contact?
If aliens are at all like us, and their conception of the universe broadly overlaps with ours, it’s a safe bet they’d look for signs of life on the same planets we’re looking for signs of life: rocky ones in the biochemistry-friendly “habitable zones” around stable stars. Rocky planets such as Earth.
All that is to say, Davenport’s team isn’t crazy to urge other scientists to point their antennas toward the SN 2023ixf supernova, and listen for the telltale signs of intelligent beings saying something.
It’s unavoidable. Given the limitations of our technology and our resources, SETI scientists have got to focus their search. “We are in a dark room, looking for any kind of light,” Ravi Kopparapu, an astronomer at NASA’s Goddard Space Flight Center in Maryland, told The Daily Beast. A SETI ellipsoid is “a really good method” of narrowing the search.
But it’s not the only method, Kopparapu stressed. Another way of prioritizing our SETI efforts is to draw up a list of the most Earth-like “exoplanets” in our galactic neighborhood—and point our radio telescopes at them for as long as we can.
Equipped with a new generation of powerful ground- and space-based telescopes, scientists are getting better and better at identifying rocky exoplanets and determining which orbit within the habitable zones of their stars. “We already know of six habitable-zone rocky planets in the solar neighborhood,” no farther than 15 light-years from Earth, Kopparapu said. “We will be discovering even more habitable-zone planets in the coming decade.”
But narrowing the SETI search pattern doesn’t have to be an either/or proposition, Kopparapu stressed. Scientists have access to around a hundred powerful radio telescopes all over the world. That should be enough to scan SETI ellipsoids and listen for signals from the directions of nearby rocky planets. “We can talk and walk at the same time.”
In any event, there’s no rush. The energy from the SN 2023ixf supernova should be radiating across our region of space for decades to come. As long as the supernova is observable, the window is open for some alien civilization to piggyback a welcome message on the star’s demise.
The same window is open to Earth scientists scanning for that message. Davenport said he’s not aware of any other radio telescopes that are currently scanning the SN 2023ixf ellipsoid for a signal from E.T. But he’s not worried. “There’s still plenty of time to join this effort!”