Are there alien probes in the solar system? If so, someone could be phoning home

For everyone who wants to believe, there is someone else questioning why no telescope or spacecraft has picked up any actual alien signals. Maybe we just didn’t know where to look.

If intelligent aliens exist, they might be trying to reach us somehow. But if they are, their signals aren’t coming through. We still have no evidence of extraterrestrial intelligence (ETI) despite some weird signals that were almost thought to be from a strange civilization until they were ruled out as false positives. Michaël Gillon of the University of Liège and Artem Burdanov of MIT think these signals could be closer than we think — somewhere in our own solar system.

Gillon and Burdanov are convinced there could be signals headed towards us right now. The theory makes more sense when you think of how young the solar system is compared to the rest of the galaxy, meaning that there was much more time for intelligent beings to evolve and develop technologies even our most imaginative science fiction writers couldn’t dream of. Their study is awaiting publication in Monthly Notices of the Royal Astronomical Society.

“If self-replicating alien probes have explored the whole galaxy, they could have formed a galactic-scale communication network based on a nodeless neighbor-to-neighbor architecture, using the stars as gravitational lenses to boost their communication efficiency,” Gillon told SYFY WIRE.

So where could these hypothetical aliens possibly be hiding? The scientists think the most likely target to watch for signals is Wolf 359, the third closest star to the Sun. It is not yet known whether there are any planets orbiting Wolf 359, or the second nearest candidate, Barnard’s star. The nearest star system to us is the Proxima Centauri system. Many scientists think its planets are unlikely to host even microbial life, never mind anything with a brain, because of the extreme radiation Proxima Centauri bombards them with. That still doesn’t mean it's a dead end in the search for ETI.

There could be forms of intelligent life as we never knew it, never even hypothesized it, that are able to withstand radiation and other deadly forces from space that would kill a human. Wolf 359 is still a better candidate than Proxima Centauri. If such aliens were to use stars as gravitational lenses for their probes, the Sun would be one of those lenses. You need to put the transmitter (Focal Interstellar Communication Device or FICD) opposite of the target star relative to the Sun. It also needs to be at a the right distance so the Sun can magnify objects out there.

“The light rays emitted by the transmitter and grazing the Sun would then be bent by its gravitational field, and a fraction of them is focused on a receptor positioned behind the target star as seen from the Sun,” said Gillon.

Now this is where Earth comes in. Either our planet or a space telescope should pass in the direction the beam is headed for us to actually detect it. The FICD needs to be in Earth’s orbital plane, and from the point of view of that FICD, Earth has to appear as if it is just barely touching the Sun. The only star that would make this possible — if a beam were emitted from that star — is Wolf 359. Say aliens do exist in the Milky Way, that could mean they have already devised an entire communication system by launching self-replicating probes to the nearest stars.

To them, we’re the aliens. But even if they are waiting to hear from us, do we have the right equipment to detect a signal, or at least will we in the near future? The most difficult part of this is to get an idea of what the emission signal is and to be sure a space telescope is in the right place to receive the signal. If a space telescope, such as the James Webb Space Telescope that is launching soon, has enough sensitivity to wavelengths of light streaking through the universe from far away, Gillon thinks they might not be too faint for it to catch a glimpse of.

“The most obvious energy source for the FICD is stellar light,” he said. “It could use a solar sail to keep the right position relative to the Sun, and solar panels to gather energy required for its emission. FICD need a constant energy source, and there is nothing better than a star for that.”

How far from the Sun is too far to detect? Maybe there is an alien civilization somewhere, but so distant that the light from its probe has yet to reach us. Only the aliens know for sure.