Search for extraterrestrials: Only very specific constellations are promising
When we look for signals that extraterrestrials send to their space probes, we should look at certain constellations, says a research team.
The presentation of the earthly signals to our space probes shows why most of them cannot be found.
(Image: Zayna Sheikh/Pennsylvania State University)
When searching for technosignatures, i.e. traces of technologically advanced extraterrestrial civilizations, we should focus on exoplanets that obscure each other from our perspective. At least that is the opinion of a research team from the USA, which has examined where our terrestrial signals would be best received. They focused on messages that we send to interplanetary probes. Outside our solar system, these could only be found if the Earth were to pass behind another planet in the solar system. Then you could detect the signals that we send to orbiters on Mars, for example, and pass it. In our searches, we should therefore concentrate on such constellations in nearby star systems.
Probability of a find mostly low
The team led by Jason Wright from Pennsylvania State University analyzed data from NASA's Deep Space Network from the past 20 years. The network consists of huge radio antennas distributed around the world, which the US space agency uses to maintain contact with the Voyager probes, for example. From there, some of the strongest and most continuous signals went into space, which is precisely what we would look for in the case of possible extraterrestrial civilizations. The team discovered that the signals are mainly sent to spacecraft near Mars, as well as to other planets and research instruments at the so-called Lagrange points, where there is a balance between the Earth's gravity and the sun. The James Webb space telescope is located at one of these points.
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Based on the results, the team has determined that possible extraterrestrial civilizations would still be able to find our signals up to 23 light years away if their technology were comparable to ours. However, the probability of this happening would be minimal – except if the search were conducted from our perspective right behind Mars. There, the probability of finding our probe communication would be 77 percent. Behind the other planets in the solar system, it would be 12 percent. This means that there are so few signals in all other directions that detection would be extremely unlikely. The team believes that we should learn from this in our own searches.
To increase our chances of finding extraterrestrial civilizations, we should therefore specifically search for signals in such constellations, the team writes. So far, however, we are not aware of many star systems with two or more exoplanets. However, this will change with the commissioning of the Nancy Grace Roman space telescope, "so that our potential search area should increase significantly". The next step for the research group is to determine which star systems have received our own signals particularly frequently. When searching for extraterrestrials, they recommend that others give preference to star systems up to 23 light years away, whose exoplanets pass in front of the stars. They have published their work in the Astrophysical Journal Letters.
(mho)
