Universe Today
With new technologies come new opportunities. And that is especially true in astronomy - with every new advanced telescope we have the potential to see (or in some cases, listen) further and more clearly than we ever have before. That is certainly the case for the new Square Kilometre Array (SKA), which is currently undergoing a multi-year roll out phase. Despite that drawn out process, astronomers are already excited about its potential, and a new book chapter from Dr. Chenoa Tremblay and her co-authors details how this new technology could be used to answer one of the most fundamental questions - are we alone?
The Search for Extraterrestrial Intelligence (SETI) has always been constrained by its resources. This constraint required researchers to focus mainly on tight signals such as the narrow band between hydrogen and hydroxyl. Early SETI pioneers justified this by claiming that such a narrow beacon would be a clear signal of intent. However, it also meant that they were only able to find signals that were intentionally sent in our direction. And the likelihood of that happening is miniscule compared to the chances there were advanced civilizations that did not feel the need to reach out to us.
Enter the SKA. Its design, which spans two continents (Australia and Africa) allows it to scan an absolutely gigantic amount of the sky. Critically, this will enable it to pick up “leakage” radiation. The authors calculated that one hour of observational time on the SKA itself would be enough to pick up signals from the equivalent of a modern-day mobile phone network similar to what we currently have on Earth from an exoplanet four light years away.
Fraser discusses the idea of unintentional transmission.That is a massive step change in our ability to detect unintentional emissions. But actually getting the time to do so is a huge part of the challenge. Telescope time on world-leading instruments like the SKA is notoriously difficult to get. So SETI researchers came up with a productive solution - they will simply piggy-back off of the data the SKA is already collecting for other surveys, such as watching supernovae or bright radio galaxies.
Duplicating radio data is easy enough - so the SETI researchers plan to use their own data pipeline, without disrupting the instrument’s primary science mission. They can also cross-reference their data with other large catalogues, such as Gaia, to evaluate signals from potentially promising sources.
Unfortunately, the downside of that is the need for processing power. Radio receivers collect a massive amount of data, and processing that requires a boatload of resources, as anyone who ran a “SETI@Home” package in the early 2000s can tell you. This leads to disasters like potentially interesting signals being discarded preemptively if not analyzed properly quickly, since the cost of storing such data for long periods is prohibitively expensive.
Fraser discusses the various ways we could find aliens.Another downside of doing radio astronomy on the Earth is the massive amount of interference coming from our own sources. Differentiating between an alien signal coming from light years away and an airplane that just happens to be broadcasting as it's flying over the Outback is a difficult challenge that the SKA researchers will tackle with two primary tools.
First, perhaps unsurprisingly, is AI. Developing an algorithm to filter out “human” radio frequency interference (RFI) will be key to any distinction of an alien signal. AIs can learn the complexities that would differentiate human-created signals from extraterrestrial ones - at least in theory.
But to support those AI models, the plan is to use a technique called Very Long Baseline Interferometry (VLBI). Essentially, this technique uses very widely spaced receivers placed far away from each other on the Earth’s surface, while that distance would barely be a blip on the scale of a signal coming from another solar system.
While all these techniques still need to be proven operationally, the time is coming when they will get to be. It’s also still unclear that the SKA will find anything that looks like an alien signal. But even a negative result in this case would be a huge data point for science more generally. And if all it takes is some data parallelization and distributed computing time (preferably with interesting graphics) to provide more insight into one of the most interesting questions in astronomy, that sounds like a win-win.
Learn More:
C.D. Tremblay et al. - Searching for Extraterrestrial Intelligence with the SKA
UT - The Square Kilometer Array has Gotten the Official Green Light to Begin Construction
UT - If Aliens Were Sending us Signals, This is What They Might Look Like
