When the SETI project searches for signs of extraterrestrial intelligence, most imagine huge radio telescopes pointing toward distant stars. But this time the scientists They turned their instruments toward something much closer: an object passing through our own solar system.
It’s called 3I/ATLAS and it’s only the third confirmed interstellar visitor we’ve observed. It arrived from another star system, crossed the solar neighborhood and, for a few weeks, became one of the most interesting targets for astronomers around the world. But now, not only astronomy experts have decided that it deserves their interest, but also SETI, the Extraterrestrial Search Institute. And the question is inevitable: because? Is there any reason to suspect extraterrestrial technology?
The short answer is no, but the long answer is much more interesting than a statement. Since the space age began, astronomers have observed millions of asteroids and comets. Almost all of them have something in common: they were born around the Sun, but 3I/ATLAS is different. Its trajectory shows that it comes from interstellar space and that it is not gravitationally linked to our star. He is a visitor from another planetary system, a true time capsule formed around a sun different from ours.
Before him we had only identified two similar cases: the famous ʻOumuamua in 2017 and comet 2I/Borisov in 2019. Each of these visitors represents an extraordinary opportunity to study materials formed around other stars. But it also raises a question that, although improbable, is scientifically legitimate. What if one day one of those objects were not natural?
The key to understanding SETI research lies in two probes launched almost half a century ago. The Voyager 1 and Voyager 2 spacecraft left the planetary region of the solar system years ago and continue traveling towards interstellar space. Someday they will pass close to other stars.
From the point of view of a hypothetical alien civilization, Voyagers would be artificial objects from another star system. That is, exactly the kind of interstellar visitor we might encounter someday.With this in mind, a team led by Sofia Sheikh, published a study in The Astronomical Journallead author of the study, focused on explaining why it is important to understand what natural interstellar objects are like in order to recognize an anomaly if one ever appears.
To investigate 3I/ATLAS, Sheikh’s team used the Allen Telescope Array, a network of radio telescopes located in California. For more than seven hours they examined frequencies between 1 and 9 gigahertz in search of extremely narrow and ordered signals.the type of emissions that nature does not usually produce spontaneously. The result was an avalanche of data.
The algorithms detected about 74 million candidate signals. After eliminating interference from telephones, satellites, terrestrial transmissions, and other human sources, only about 200 cases remained worthy of detailed review. They all ended up having a conventional explanation. There was no alien message, no interstellar beacon, no alien ship hidden inside the object.At first glance, the study appears to have concluded with a negative result.However, for Sheikh it is just the opposite.
The observations made it possible to rule out the presence of relatively modest radio transmitters, of only between 10 and 110 watts, a power comparable to that of many domestic appliances. This means that current systems are already capable of putting very precise limits on possible extraterrestrial technologies. In short: if there are signs of other civilizations, we have a way to detect them.
3I/ATLAS is probably exactly what it sounds like: a comet or icy body formed around another star billions of years ago. Astronomers believe that in the coming decades we will discover many more interstellar visitors thanks to new generations of telescopes. Each of them will be an opportunity to study other planetary systems without leaving our own. And each will offer an occasion to test one of humanity’s oldest questions. Are we alone?
For now, 3I/ATLAS has not provided any evidence of extraterrestrial intelligence. But for him SETI has served to demonstrate something just as important: when the next interstellar visitor appears, we will be ready to listen to it.