SETI Astronomers find two potential technosignatures after examining 12 exoplanets

(NASA's Goddard Space Flight Center/Chris Smith https://bit.ly/3C9ymJY)

Astronomers from the SETI Institute searched for artificial radio signals from 12 transiting exoplanets that could send them during a transit event.

The team led by Sofia Z. Sheikh found two interesting candidates, which, however, are highly likely to be man-made RF interference.

The question of whether life, especially intelligent life, exists outside the Earth still remains unanswered.

One way to find the answer to it is to look for technosignatures, such as artificial radio signals that would come from exoplanets.

The generation of such signals requires significant energy costs.

So, it is logical to assume that their properties should be obvious and convenient for both the signal sender and its potential recipient, who do not know each other.

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SIGNAL
Now, Sheikh’s team published the results of a search for narrow-band, frequency-drifting radio signals from 12 exoplanetary systems.

The SETI Institute astronomers used the 100-meter Green Bank Ground-based Radio Telescope on March 25, 2018 in the frequency range 1.1-1, 9 GHz.

The observations covered a total of 6 hours, the calibration was carried out in the course of observations of quasars, pulsars and the famous Tabby star.

The target systems were selected from 540 exoplanets that make transits across the disks of their stars from the point of view of an earthly observer.

All 12 selected exoplanets are located relatively close to each other in the sky

They were discovered by the Kepler space telescope and are bodies with

• radii of 0.79–12.19 Earth radii
• equilibrium temperatures of 510–2080 kelvin
• located at a distance of 120–992 parsecs from the Sun.

The researchers didn't consider the potential habitability of the observation targets.

Scientists proceeded from the fact that the moment of transit of a planet with a source of radio signals across the disk of its star can serve as the Schelling point

This means that if the source sends a signal when the planet is in the middle of the transit, then any recipient of the signal will fix it and observe in that direction.

Since this phenomenon is strictly periodic in nature, we can conclude that it is artificial.

The scientists identified 34,000 possible candidates for technosignatures, but further analysis excluded most of them, leaving only two interesting cases.

The first signal came from the exoplanet Kepler-1332b at a frequency of 1749 megahertz, and the second came from the exoplanet Kepler-842b at a frequency of 1040-1438 megahertz.

None of these signals are narrowband, but they were bright enough.

However, officially both candidates so far remain candidates not for technosignatures, but for broadband man-made radio frequency interference.

If repeated similar signals are not recorded from exoplanets Kepler-1332b and Kepler-842b in the future, this will mean that all 12 targets do not emit transit signals in the range of 1.1–1.9 GHz.

We will be looking forward to solving the mystery.

Sources:

• Arxiv: https://arxiv.org/abs/2212.05137
• Phys.org: https://phys.org/news/2022-12-astronomers-scanned-planets-alien-front.html

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