📡 Extraterrestrial technosignatures: we've been wrong from the start

According to an analysis, it is plausible that technosignatures, messages of extraterrestrial origin, have already passed by Earth but gone completely unnoticed. While the hunt for signals of extraterrestrial origin generally focuses on our galactic neighborhood, new research challenges this localized approach.

Physicist Claudio Grimaldi used a statistical method. His model evaluates how many artificial signals should have crossed our planet since the start of research programs for a discovery to be probable today. This calculation framework takes into account several parameters, such as the presumed longevity of the emissions and the capabilities of our instruments.


The detection potential appears most favorable when extending the field of observation to great distances, beyond the few hundred light-years usually observed. If technological emissions are sufficiently persistent and widespread in the Milky Way, signals coming from several thousand light-years away could be identifiable.

These observations guide projects like SETI towards new strategies. The goal is to prioritize observations covering vast portions of the galaxy over extended depths, of several thousand light-years. The constant improvement of instrumental technology plays a major role, as it gradually allows the capture of fainter or unexpected types of emissions.

The model, published in The Astronomical Journal, takes into account both signals broadcast in all directions and directional emissions, such as laser beams. This unified method provides an estimate of the probability of contact based on the longevity of the signals and the performance of our detectors. It highlights that the absence of a discovery to date does not necessarily mean the non-existence of technological civilizations.

Instead of focusing solely on nearby stars, it might therefore be necessary to systematically examine large volumes of space. This method would considerably increase the chances of stumbling upon a signal.

Technosignatures: footprints of distant technologies

A technosignature designates any observable trace that could indicate the presence of advanced technology beyond Earth. This includes artificial radio transmissions, laser pulses, or even the heat produced by large constructed structures. These signals travel at the speed of light and can persist for highly variable durations.

The identification of these footprints relies on two main conditions. First, the signal must reach our planet. Second, our instruments must be sufficiently sensitive and correctly oriented to identify it. A signal can go unnoticed if it is too weak, too brief, or emitted on a frequency not being monitored.

The quest for these signatures is not limited to intentional messages. It also encompasses indirect phenomena, such as the modification of a planet's environment or the presence of artificial objects in orbit.

While most are ephemeral, capturing them would require a great deal of luck. If some are long-lasting, they could be detectable even at great distances, offering a wider window for observations.