This article is taken from the monthly Sciences et Avenir – La Recherche n°907, dated September 2022.
It is the most mysterious star in the galaxy: located 1480 light-years from the Solar System, Tabby’s Star (KIC 8462852) is suspected by some astronomers to be surrounded by a “Dyson sphere” – a gigantic energy-harvesting megastructure built by an extraterrestrial civilization. Far from being verified, this hypothesis would nevertheless explain the seemingly incomprehensible signals it sends us.
Signals first captured by the Kepler space telescope. Launched in 2009, this NASA instrument observed the light variations of 150,000 stars in the Cygnus constellation for four years, allowing it to detect the presence of more than 2,000 exoplanets. These were identified using the so-called transit method: the periodic decrease in the brightness of a star is associated with the passage of a planet in front of it. The effect of the transit of a planet on the brightness of a star is actually very weak: the passage of a body like Jupiter in front of a star similar to the Sun leads to a decrease in apparent brightness of about 1%, and for a Gemini Earth only 0.001 %.
Flow reductions of up to 22%!
To sift through the vast amount of data collected by Kepler, the researchers first called for volunteer planet hunters by soliciting the online citizen science group Planet Hunters. It was these amateur astronomers who were first struck by the amazing light curves of KIC 8462852, a star slightly more massive and brighter than the Sun. These graphs actually showed decreases in flow of up to 22%! Which ultragiant planet could eclipse a fifth of a star’s luminosity? “Planet Hunters volunteers then contacted the science team to find out what could be causing these strange sightings. “, recalls Tabetha Boyajian, an astrophysicist at Louisiana State University (USA), who took the lead in research on this star since it was called “Tabby’s Star”.
This stellar object is all the more exciting because its dips in brightness are not periodic and can last from 5 to 80 days before returning to normal. It is therefore impossible to explain them with the passage of a planet. In 2016, Louisiana State University astronomer Bradley Schaefer revealed that by studying archival data, including old photographic plates, he was able to show that the brightness of KIC 8462852 had already decreased. 14% between 1890 and 1989.
A few months later, a study published by the American astrophysicists Joshua Simon of the Carnegie Institute in Washington and Benjamin Montet of Caltech in Pasadena further complicates the matter. It shows that during the four years of observation of the region by Kepler, the star’s brightness gradually weakened, with a 1% decrease in brightness in the first three years and then 2% in six months, before stabilizing during the last six months of observation. To explain this, the two researchers hypothesize that a collision between two planets orbiting the star could have caused the sudden 2% drop in brightness. Or the explosion of a comet in Kepler’s line of sight.
But the infrared analysis of the star and its environment by Tabetha Boyajian’s team then ruled out these hypotheses, as well as those about the presence of dust clusters or planets forming around it. The only natural explanation that has not yet been ruled out is the possible presence of a swarm of large comets or planetary debris that would block the light from the star as it passed in front of it.
The hypothesis of an extraterrestrial infrastructure always makes the most daring dream
In 2021, the study sees a new twist: new data published by researchers from the University of Arizona (USA) show that Tabby is gravitationally connected to a small companion star, a red dwarf 132 billion miles away. But nothing yet proves that this distant body is the origin of the described oddities. “To this day, there is still no widely accepted theory as to what is behind this star’s strange behavior. Tabetha Boyajian concludes.
So the hypothesis of an extraterrestrial infrastructure always makes the most daring dream. Described in a 1960 scientific paper by American physicist Freeman Dyson, the artificial sphere would surround a star to capture its energy more efficiently. A Dyson sphere built around the Sun would thus receive nine times more energy than that intercepted from Earth. Such a device would serve a Type II civilization according to the Kardachev scale. Proposed in 1964 by the Soviet astronomer Nikolai Kardachev, the latter predicts that a Type I civilization is sufficient with the energy available on its planet (4 x 1016 watts), while that of Type II would have to consume energy directly. (4 x 1026 W). An article published in 2020 by American astronomer Robert Gray classifies our Earth civilization as type 0.72 as of 2015. The inhabitants of the Tabby star system, if they exist, would therefore belong to a much more advanced civilization than ours.
Although no program devoted to the search for hypothetical extraterrestrial signals has produced results to date, it is clear that an increasing number of unidentified flying objects have been reported since the early 2000s, as indicated in May, Scott Bray, Deputy Director of Intelligence for the US Navy, before the US Congress. He carefully specified that nothing could indicate an extraterrestrial origin for these phenomena, without further ruling out that…
To date, dozens of unexplained phenomena have been observed by military pilots. Drones, birds, new military equipment tested by the Russian or Chinese armies? Whoever they represent to the leaders of the US Army “a potential threat to national security and air traffic The US Department of Defense has therefore launched a new program to document unexplained phenomena and identify experimental “weapons” potentially deployed by belligerent powers.
Excerpt from a video taken in 2004 by a US fighter jet showing an unidentified flying object (black spot). Credit: US DEPARTMENT OF DEFENSE
NASA launches large-scale survey
The US Army was soon joined on this ground by NASA. Purpose: to initiate solid research on the subject because “the scientific process is valid for dealing with all problems, including this one “, said Thomas Zurbuchen, associate administrator at NASA. This large-scale study will be led from the beginning of the school year and for nine months by astrophysicist David Spergel, specialist in the cosmic background at Princeton University (USA). It will be a question of to collect a maximum of data and evidence and to develop scientific tools to analyze them and thus determine their nature and their origin, extraterrestrial or not, in the hope that the inexplicable signals will not remain so forever.
First detection of “little green men”
In 1967, Irish Jocelyn Bell was a student at Cambridge (Great Britain). She is working on the realization of a radio telescope intended for the study of the scintillation of quasars, the most luminous sources in the universe. Examining the data from the instrument, she discovers a signal that repeats itself with metronome regularity every 1.3 seconds! A message from those aliens, the team immediately thinks. Who christens the signal with the name Litte Green Men 1 (LGM or Little Green Men 1).
But before proceeding on the world stage with such a resounding announcement, it is necessary to check whether the message can have a natural origin. Returning to her work, Jocelyn Bell then discovered a new, similar source at a distance from the first. Could this be a new class of celestial bodies? Astronomers have since shown that the little green men are actually fast-spinning neutron stars, called pulsars. Today, all these spinning stars are listed under the acronym LGM: little green men!