(Artistic representation of a Dyson Sphere / Wikimedia Commons https://bit.ly/3e1DYfQ)
A team of Chinese astronomers has concluded that the unusual narrow-band radio signal recorded in the direction of an exoplanet is not a technosignature, but from human origin.
Are we alone in the Universe? To answer that question scientists are looking for signs of life outside the Earth in several ways.
For example they explore and discover exoplanets, looking for biosignatures in their atmospheres.
They also study interesting (from the point of view of astrobiology) bodies of the solar system.
Scientists also search for technosignatures, observing the sky using the SETI (Search for Extraterrestrial Intelligence) program.
The SETI program has been operating since the 60s of the last century, and uses radio telescopes to survey the sky in search of possible artificial radio signals (most often narrow-band) from other star systems.
In recent years, due to the ever-increasing number of known exoplanets, SETI observations have increasingly targeted specific stars around which potentially habitable exoplanets orbit.
THE STUDY
Now, a team of astronomers from the Institute of Astronomy at Beijing Normal University published the results of target observations.
The group, led by Zhen-Zhao Tao, worked under the SETI program from April to September 2021 using the 300-meter FAST radio telescope in China.
The giant telescope is equipped with a 19-beam cryogenically cooled receiver, which provides a very high sensitivity.
The targets were 33 star systems containing known exoplanets.
(Sources with planets in the habitable zones are denoted by blue symbols. / Zhen-Zhao Tao et al. / arXiv, 2022 https://bit.ly/3Cy8bxz)
They are mostly considered to be rocky and lie between 3.37 (Ross 128b) and 219.6 (Kepler-296b) parsecs from the Sun.
Scientists were looking for narrow-band drifting signals in the frequency range of 1.05-1.45 gigahertz, which could be technosignatures.
The vast majority of detected signals are obvious radio interference, or cases of false alarms.
THE SIGNAL
However, last year scientists identified an unusual signal at a frequency of 1140.604 megahertz during observations of the red dwarf Kepler-438.
This particular stellar system has an Earth-like exoplanet near the edge of the habitable zone (where liquid water could exist).
The properties of the signal, such as the width and speed of the drift, as well as registration in only one beam, made it look like a technosignature.
However, after analyzing the data, the Chinese scientists came to the conclusion that the polarization properties of the signal can rule out the possibility of its extraterrestrial origin.
The signal must come from anthropogenic radio frequency interference.
Additional observations of Kepler-438 were made using FAST on November 7, 2021, as well as on March 10, 19 and 28, and April 6, 2022, but no other signals were recorded.
So far, we’re still alone in the Universe.
Source:
- arXiv.org: https://arxiv.org/pdf/2208.02421.pdf
- Astrobiology: https://astrobiology.com/2022/08/sensitive-multi-beam-targeted-seti-observations-towards-33-exoplanet-systems-with-fast.html
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