Are we alone in the universe? There are good reasons to suspect that we have company.
After all, the universe is exceptionally large, with possibly billions of Earth-like planets in our Milky Way galaxy, which is but one of trillions of galaxies in the universe.
The ingredients for life, as far as we know, are common. And humans on Earth have proven life is capable of evolving to a point of technological complexity which could make our presence visible to anyone out there looking.
But could we recognize such a signal if it floated past our planet? Researchers are deploying new technology to aid us in that ongoing search.
The Search for Signs of Intelligent Life in the Universe
Astronomers have been listening to the stars for decades hoping to detect signals in the electromagnetic spectrum from a technologically advanced civilization.
The SETI (search for extraterrestrial intelligence) Institute has been responsible for a lot of that listening. And new software developed by SETI investigators is helping them search for more sensitive signals than they ever have before.
“We don't have a clear idea about the exact types of signals that might exist out there,” says Vishal Gajjar, an astronomer at the SETI Institute and project scientist for the Breakthrough Listen program. “So, we aim to search for various types of techno-signatures — indicators of advanced technology — that could be out there in space,”
Beacon Signals of Extraterrestrial Life
SETI efforts have honed in on what they call “beacon” signals. These are a type of signal that an intelligent civilization might create to indicate to other potential lifeforms that they exist, and that they are open for visitors.
Such signals should be easily distinguishable from naturally occurring phenomena in the universe and are uniquely designed to stand out against the cosmic background. If we were to ever detect such a signal, we could assume with a high likelihood that it could be coming from an intelligent source.
Gajjar says SETI prefers to look out for beacon signals because they have a higher probability of being discernible in the vastness of space: “By targeting beacons, we increase our chances of identifying potential techno-signatures and advancing our quest to uncover signs of extraterrestrial intelligence.”
New Possibilities for SETI
SETI’s new software, namely the fast-folding algorithm (FFA), which Gajjar helped to develop, is designed to analyze data collected by radio telescopes for characteristics of these beacon-type signals.
Technically speaking, the FFA technique helps search for periodic signals with shorter duty cycles, something that is hard to capture via previous methods.
“To put it simply, if a signal only lasts for a brief moment, like a few tens of milliseconds, and then repeats every few tens of seconds, it becomes difficult to detect using traditional methods,” Gajjar says. “By utilizing the FFA we enhance our ability to detect and recognize these short and elusive signals.”
Hunting for Different 'Alien' Signals
Previous SETI efforts have focused primarily on detecting continuous signals in the narrowband that persist over time, since nature alone doesn’t produce narrowband signals.
However, the new software enables researchers to look out for pulsating narrowband signals, which compared to continuous signals are more energetically efficient and therefore might be a better option to use as a beacon.
This insight has allowed researchers to look for a new class of techno-signature signals.
While it might be more realistic for SETI investigators to identify a beacon signal, there is another class of signals that could indicate the presence of an intelligent, technologically advanced civilization. These are called “leakage” signals.
Instead of sending out a cosmic beacon to other intelligences in the universe, it may be that we pick up the signals from activity of an alien civilization that was not meant for us. Think of it like interstellar eavesdropping.
But leakage signals might be harder to identify than beacon signals for several reasons. As human communication techniques have evolved, we have made our signals more robust against other electromagnetic noise, which in turn can make our signals more challenging to interpret (if you don’t have the right information to decode them). This might also be the case for any other intelligent life trying to communicate.
“They might employ highly complex signal modulation methods that, to a common observer, could resemble noise,” Gajjar says.
Lack of Knowledge About Alien Technology
It’s also difficult to identify leakage signals when you have no prior knowledge about the types of communications tools currently or previously used by these potential life forms, Gajjar adds.
“Without prior information, we may struggle to distinguish these signals from background noise or other natural phenomena. The complexity and sophistication of the signal modulation can make it harder to recognize patterns or intentional transmissions,” he says.
As such, the new software will help astronomers like Gajjar search the cosmos in ever more detail for signs that we are not alone. Meanwhile, they will also continue the search for more recognizable beacon signals and overt ways that life beyond might be trying to get our attention.