Astronomers hunting for aliens find new way to work out when they would contact us
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Astronomers hunting for aliens and trying a new technique to work out exactly when they would contact us.
The research uses ideas from game theory to predict not just where extraterrestrial civilisations would message us from, but when they would do so.
The work – led by scientists from the SETI Institute, a non-profit that searches for alien life – is based on the idea that we would not only need to point our telescopes at the right part of space to pick up messages from aliens. We would also need to be listening at the right time, to avoid missing it.
The work is based on the idea of the “Schelling point”, an idea from game theory based on working out the choice that two parties would make independently, without being able to co-ordinate. Two people who had decided to meet up in New York City but were unable to get in contact with each other might choose to meet in Grand Central Station at noon, for instance, since that is likely to be chosen separately by the other person without being able to co-ordinate.
The scientists are looking for a similar place and time for contact from alien civilisations. They have focused their work on the anti-solar point, a specific part of the sky that another alien world might choose on its own.
The new work did not yet pick up any signals from alien intelligence. But it already offers a breakthrough: it represents both the first observational search of that part of space, as well as a potential start of a new approach for hunting for alien life that could one day pick up such signals.
To choose the right part of space, astronomers borrowed an idea that we have already used to find distant planets. When a world passes in front of its star, observers can see it in a process called a “transit”, which briefly dims the light from that star and shows not only that the planet exists but also can be used to understand its orbit and where it is in relation to its star.
To an alien civilisation doing the same sort of work with Earth, our planet would also be right between them and our Sun. From Earth, the planet would appear in the complete opposite direction from the Sun, which is known as the anti-solar point.
That means that both we and any theoretical alien civilisation that was observing us would be able to pick a specific part of space, without being able to communicate, and so could each independently recognise that alignment. It could therefore be a useful way of co-ordinating communication without already being able to send messages to each other.
The scientists note that there is nothing to suggest that an alien civilisation would choose to use this point, or certainly that they are already doing so. But it offers a new way to think about how we try and search through space for aliens, they said.
“The challenge in SETI isn’t simply deciding where to point a telescope,” said Sofia Sheikh, SETI Institute research scientist and co-lead author of the paper.
“It’s figuring out where and when another civilisation might choose to transmit. The anti-solar point gives us a way to think about that problem from the perspective of a potential sender, rather than just the receiver.”
Usually, SETI searches pick a particularly exciting star, or the planetary systems around them. The new research takes a new route, not picking a specific target but instead looking using a particular alignment that might also be worked out by those distant worlds.
Researchers are already trying out the theory using the SETI Institute’s Allen Telescope Array (ATA) at the Hat Creek Radio Observatory in Northern California. They plan to do so two or three nights each week, allowing them to cover all the important parts of the Earth’s orbit over four years.
That will give huge amounts of data, making it hard for scientists to pick through it in search of useful signals. As such, they have built an automated process that is able to look for “technosignatures”, or evidence of possible alien technology, in the data – filtering out potential distractions such as radio interference from our own communication systems.
Before that big campaign started, the team did three night survey to try out whether it would work, during the summer of 2023. They gathered 32 terabytes of data over 17 hours of observations – which led to about 1.9 million detections, all of which could be explained by interference from human sources.
But that disappointment has given the researchers useful data about how to filter out those signals, as well as improving their methods for finding signals in specific directions. It also allowed them to work out how far a signal might be able to make it through space to reach us, suggesting that if they had a transmitter as powerful as Earth’s now decomissioned Arecibo radar we could hear from them over 124 light years.
The work is described in a new paper, ‘A Large-Scale Technosignature Survey of the Anti-Solar Point with the Allen Telescope Array: Survey Design and Pilot Results’, published in The Astronomical Journal.
