00:00NASA is on the hunt for Dyson spheres.
00:04Indeed, it has been found that 60 stars had unusual luminous patterns,
00:09which could indicate the potential presence of an alien technology nearby.
00:15A team of researchers has developed a new method to detect advanced civilizations by searching for Dyson spheres.
00:23All life forms, whether simple microbes or humanity, need energy to survive.
00:29As species evolve, their energy needs increase.
00:33We first used fire, then coal and oil, before moving on to solar panels.
00:39Imagine now an extremely advanced civilization, having exhausted all the energy sources available on its planet.
00:46What could be the next solution? Their high star, which constitutes an almost infinite source of energy.
00:53This is where the concept of Dyson spheres comes in, proposed by physicist Freeman Dyson in the 1960s.
01:00This concept envisages the construction, in theory, of a gigantic structure around a star in order to capture its energy,
01:08like a huge solar panel.
01:10Such a technology could allow advanced civilizations to meet the energy needs of their planet,
01:17and even feed interstellar travel.
01:21At present, such a project remains out of reach for humanity.
01:25However, it is conceivable that another civilization in the universe has already succeeded in realizing it.
01:33Scientists have collected a considerable amount of data from star surveys,
01:38analyzing more than 5 million objects to identify some potential candidates.
01:43But it goes without saying that extraterrestrial civilizations could use radically different technologies.
01:49Thus, instead of looking for huge structures around stars, astronomers focus on the search for technosignatures.
01:57These clues are unusual phenomena likely to indicate a technological activity
02:02that cannot be attributed to known natural sources, such as galaxies or nebulae.
02:08For example, a structure like a Dyson sphere could emit an atypical infrared radiation
02:14due to the considerable heat it would release by absorbing the energy of a star.
02:19Among the millions of objects studied, 368 were considered potential candidates,
02:24and a more strict filtering allowed only 7 to be preserved, which could correspond to Dyson spheres.
02:31Usually, such unusual infrared radiation results from violent events in space,
02:37such as planetary collisions, which scatter dust and fusion splinters while producing irregular luminous patterns called debris disks.
02:46Researchers estimate that these 7 objects could be M-type stars, known as red dwarfs,
02:53which are smaller and less luminous than our sun, which is a yellow dwarf.
02:58Stars of this type generally do not have dust or debris in orbit around them.
03:03However, additional analyses, including an in-depth study of the light emitted, are necessary to confirm this hypothesis.
03:12Another study identified 53 stars with an excess of similar infrared radiation, which must also be closely examined.
03:20Scientists consider using sophisticated instruments, such as the James Webb Space Telescope,
03:26to analyze in detail all of these candidates.
03:30A particularly famous candidate is the star of Tabby.
03:33Scientists have even given it a comical nickname, inspired by the title of the article dedicated to it.
03:39Where's the flux?
03:41It's up to you to imagine the acronym.
03:43This star is a little warmer and more massive than our sun.
03:47It has retained NASA's attention due to its unusual and irregular luminosity variations.
03:54Indeed, instead of shining in a stable way, it seems to blink, like a flashlight that would be turned on and off cycle after cycle.
04:02At first glance, one might think that this is due to the passage of a large planet or a comet in front of the star.
04:08However, the drops in luminosity reach up to 22%.
04:12No planet would be able to mask a quarter of the light of a star, hence the intriguing nature of the phenomenon.
04:20Another hypothesis advances the idea of a Dyson sphere, or a similar megastructure.
04:25Some have also suggested that these variations could be due to fragments of a disintegrated exolune orbiting the star.
04:32Although other stars present comparable phenomena, no tangible evidence can confirm these theories.
04:39For now, scientists remain in uncertainty.
04:43Astronomers are therefore in search of any gigantic structure likely to exist.
04:48The forms that a Dyson sphere could take are multiple.
04:52Rings, bubbles, satellites, gigantic shells, and many more.
04:57A Dyson shell, for example, would consist of a rigid envelope completely surrounding the star.
05:03This option represents the most extreme and also the most complex solution to realize.
05:08If an advanced civilization had actually built such a structure, it would completely block the light of the star, making it invisible to our eyes.
05:18The inner surface of this shell could be arranged in habitats,
05:22and gravity could be simulated by rotating the entire structure around the star.
05:27A Dyson sphere, on the other hand, would be the most accessible option.
05:31A network of satellites and habitats collecting energy in orbit around the star.
05:36This environment could be the most pleasant,
05:39the inhabitants living in a set of space stations or small houses scattered within the sphere.
05:45Each habitat would have its own subsistence system, with air, artificial gravity, and the necessary infrastructures.
05:53It would also be possible to grow crops there.
05:56And the view would be spectacular.
05:58A sky always bright, constelled by other habitats visible through the immensity.
06:03With the energy almost unlimited of a star available,
06:06we could accelerate our development, produce huge amounts of material,
06:10and even terraform planets of the stellar system.
06:13But the construction and maintenance of a Dyson sphere
06:16would require cutting-edge robotics technologies and colossal financial resources.
06:21Such a project would take centuries, even millennia, before being realized.
06:26Megastructures are not the only paths explored by scientists in their quest for extraterrestrial life.
06:32Planets are also carefully scrutinized.
06:36To be considered as potential habitats, planets must have certain characteristics.
06:42In particular, the presence of liquid water,
06:44as well as a source of energy capable of triggering the necessary reactions
06:48to the formation of the constitutive elements of life.
06:51It turns out that these conditions are not particularly rare.
06:55Our research suggests that there could be more than 60 billion potentially habitable planets,
07:00just within the Milky Way.
07:03However, we are not able to observe them directly or send missions there.
07:07So we have to use stratagems,
07:10such as detecting the presence of water and certain gases conducive to life in their atmosphere.
07:14Recently, the James Webb Space Telescope
07:17has detected clues suggesting the presence of life on a planet called K2-18b,
07:23relatively close, about 120 light-years from Earth.
07:27This planet is nine times larger than ours and has clouds of liquid water,
07:31although its atmosphere is different,
07:33with gases such as methane, carbon dioxide and dimethyl sulfide.
07:38A form of life requiring oxygen would have trouble prospering there,
07:42but on Earth, this sulfur is mainly produced by living organisms such as phytoplankton.
07:47Scientists have also discovered that planets with unusual and wavy orbits
07:53could reveal the presence of advanced extraterrestrial civilizations.
07:57In our solar system, each planet follows its own orbital path,
08:02but the universe is full of surprises.
08:04According to the models, there could be planets sharing the same orbit,
08:08provided that they are arranged uniformly around the star,
08:12which would limit their mutual gravitational influence.
08:15There is also what is called the iron-horse configuration,
08:20where planets accelerate and slow down from each other,
08:24adopting sinuous trajectories.
08:26These iron-horse systems could accommodate up to 24 planets.
08:31However, this type of configuration, although theoretically possible,
08:36remains very unlikely without a form of intervention.
08:39Normally, gravity would destabilize such systems in a blink of an eye.
08:44Thus, the discovery of a stellar system where 24 planets share the same orbit
08:49could suggest the involvement of an advanced civilization.
08:52It could also be that extraterrestrial civilizations are trying to contact us directly.
08:58Extraterrestrial intelligence research began in the 1960s,
09:02when astronomer Frank Drake began to capture radio signals from space.
09:07Today, this quest continues.
09:09Astronomers are still listening to parasitic radiations,
09:13these radio waves accidentally emitted into space by current activities.
09:17Recently, radio waves have been detected from Iguazet C-Tibet,
09:22a planet located only 12 light years away.
09:25This suggests the existence of an essential magnetic field
09:28to protect life from solar radiation.
09:31However, Iguazet C-Tibet is probably too close to its star to be habitable.
09:36There are many places where such a signal could come from.
09:40Indeed, there are a thousand stellar systems in our galaxy
09:44from which it is possible to observe us.
09:47All these stars benefit from a privileged view of the Earth
09:50when it passes in front of the sun,
09:52facilitating the detection of our planet by possible extraterrestrial astronomers.
09:56Thus, more than a thousand stellar systems could be watching us right now.
10:02If we study them carefully,
10:04we might one day find evidence of an intelligent life watching us back.
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