Free Astronomy Magazine May-June 2022

35 MAY-JUNE 2022 ASTRO PUBLISHING A n outlook of the Eastern Hex at sunset, part of the Murchison Widefield Array’s Phase 2 compact configuration. [Kim Steele, Curtin University] the center of the star field framed by MWA. Several studies have shown that that monstrous object of 4.2 million solar masses has gone through periods of intense activity, during which it devoured enormous quantities of matter and emitted very intense streams of X-Ray and UV radiation. These episodes have occurred quite frequently (on an as- tronomical scale) in the history of the Milky Way and have lasted for up to tens of millions of years. A work published in Nature in 2017, authored by Amedeo Balbi and Francesco Tombesi (University of Rome ‘Tor Vergata’), showed that the ra- diation released by Sagittarius A* in those episodes was more than enough to annihilate all forms of life (as we know it) within a radius of 7 kpc, stripping Earth- like planets of much of their atmospheres. Only at distances greater than 7 kpc might life have en- joyed relatively safe and stable habitats, capable of favoring its development in ever more advanced forms, up to the pos- C henoa Tremblay is the researcher who in recent years has led several series of observations in the radio domain in search for technosignatures of alien origin. The last session targeted the galactic center. [Pawsey Supercomputing Centre] in the densely packed galactic cen- ter, stellar flybys are more likely. Those are bad news for life, let alone civilization. They can disrupt protoplanetary disks and interfere in the planet formation process.” If these were the only contraindica- tions in the search for technosigna- tures in the galactic center, all SETI programs would point in that direc- tion. The reality is far worse. Both Gowanlock and Tremblay’s team seem to underestimate a decisive presence in the evolution of our gal- axy: Sagittarius A*, that supermas- sive black hole surprisingly placed at sible emergence of a technological civilization. This is our case. The Earth is in fact 8.2 kpc (26,700 light years) from Sagittarius A*, therefore just 4,000 light years outside the critical radius, which means that looking for technosignatures in the direction of Sagittarius A* can only make sense if one hopes to find them in the first 4,000 light years from Earth. This distance is 15% of that investigated by Tremblay’s team, and if we consider that stellar density increases significantly near the galactic center, we find that of the 3 million stars theoretically ob- served, only a small part is at a safe- enough distance from Sagittarius A*. Of these, we know that only about 20% can offer the conditions neces- sary for the lasting evolution of life. On balance, it was extremely un- likely that those 7 hours of “listen- ing” could lead to the discovery of technosignatures. It is much more likely to win the Mega Millions lot- tery jackpot! Fatally, even this umpteenth SETI study could only end with the usual sad statement: “No plausible technosignatures are detected.” !