Les astronomes ont fait une découverte super cool : ils ont trouvé la lumière qui a "allumé" l'univers ! Cette lumière provient du moment où les premières étoiles et galaxies ont illuminé le cosmos il y a des milliards d'années. C'est comme retrouver les photos de bébé de l'univers, nous montrant à quoi ressemblaient les choses à l'époque. Ils l'ont repérée en utilisant des télescopes avancés capables de détecter une lumière ancienne et faible voyageant à travers l'espace. Cette découverte nous aide à comprendre comment l'univers est passé d'un endroit sombre et vide à l'espace étoilé que nous voyons aujourd'hui. C'est un aperçu du début cosmique ultime ! Animation créée par Sympa.
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Stock de fichiers (photos, vidéos et autres):
https://www.depositphotos.com
https://www.shutterstock.com
https://www.eastnews.ru
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FunTranscript
00:00Just after its creation, the cosmos was plunged into darkness.
00:04I wasn't there personally, but that's what most scientists think.
00:08All the stars were hidden behind a thick fog of primordial gases.
00:13Then, all of a sudden, something dissipated this fog and the universe began to shine,
00:18as if it had finally awakened.
00:20But how did this happen?
00:22Eight recently discovered low-light galaxies could give us an answer.
00:26The Big Bang created our world about 13.8 billion years ago.
00:31At first, there was only one soup of boiling particles, very hot and chaotic.
00:37But over time, things cooled down, and the particles ended up sticking to each other.
00:43This is how the atoms appeared.
00:45A little helium, but especially hydrogen, the very first element.
00:49These first elements created thick clouds of gas, very opaque.
00:53Then, the first stars began to form.
00:56They were incredibly bright.
00:58They emitted a lot of light, including ultraviolet rays.
01:02But despite this, a large part of their light could not spread very far
01:07because of this evil fog of hydrogen.
01:09The gas clouds absorbed and dispersed all the small particles of light.
01:14It's as if the light was trapped around the stars.
01:18This dark age lasted hundreds of millions of years.
01:22Then everything changed.
01:23Recently, the James Webb Space Telescope spotted ancient dwarf galaxies dating from this time.
01:29It turns out that they are the ones we should thank for illuminating the universe.
01:34At the time, these galaxies were filled with primitive stars.
01:38These stars emitted such a powerful radiation that they not only managed to dominate,
01:43but also to break the hydrogen atoms present in the fog.
01:47They transformed them into charged particles,
01:49into particles that carry a little electricity, called ions.
01:53Little by little, the fog dissipated.
01:56This process of fog dissipation is called rayonization.
02:01And this beautiful era is known as the Age of Rayonization.
02:05Finally, light was able to travel in all corners of the universe,
02:08which really changed things.
02:10Just like the Age of Human Light.
02:13To find these small lighters, astronomers used a technique called gravitational lens.
02:19Imagine that light travels in space like a rectilinear beam.
02:23But like everything that exists in our world, including time,
02:27light obeys gravity.
02:29If it is too strong, it will deform the luminous beams.
02:33Thus, when the beams pass near a massive object,
02:37the gravity of the object attracts them, bending and deforming their trajectory.
02:42This is why black holes look so frightening.
02:45They stretch the stars and all the space around them like whirlwinds.
02:49But it's not that scary, actually.
02:51An ordinary glass or a magnifying glass does something similar.
02:55Hence the name of gravitational lens.
02:58When the object that acts as a lens is incredibly massive,
03:02it deforms the light into multiple images of the same object,
03:05thus creating a structure that is both frightening and fascinating,
03:09which is called an Einstein ring.
03:11However, if the object is not very large,
03:14the curvature is less spectacular and slightly deforms the shape of the object in the background,
03:19making it look a little stretched.
03:21The effect of the gravitational lens also allows scientists to study the mysterious black matter.
03:28If the light seems stretched,
03:30and this stretching is not only due to the presence of massive objects nearby,
03:34it may be something invisible and heavy that curves it.
03:39Since these 8 galaxies are too dim,
03:42scientists had to resort to this gravitational trick to observe them.
03:46The researchers therefore studied the light of old galaxies,
03:49more than 13 billion years old.
03:51They focused on a galactic cluster called Abel 2744,
03:56also known as Pandora's Cluster.
03:58These discoveries allowed them to understand
04:01how these little good men played a considerable role in the transformation of the primitive universe.
04:06The James Webb telescope is an incredible tool
04:09that could soon allow us to look at even older periods,
04:13dating from the cosmic dawn,
04:15when the universe was only a few million years old.
04:18Another formidable tool, the Nancy Grace Roman Space Telescope, will help.
04:23It is also possible that these galaxies did not do all this work on their own.
04:27These first massive stars were absolutely terrifying.
04:31According to some estimates, they were 30 to 300 times more massive than our sun,
04:36and millions of times brighter.
04:38Modern stars contain heavy elements,
04:41but at the time they used the only available elements, hydrogen and helium,
04:46which explains why they were so hot and bright.
04:50But they also had a very short lifespan, only a few million years.
04:55For comparison, our sun is 4.6 billion years old,
05:00and it is still active, fortunately for us.
05:04At the end of their life, they turned into supernovas.
05:08These explosions of colored energy were so powerful
05:11that they forged the first heavy elements of our world
05:14and spread them throughout the universe,
05:17thus planting the first seeds of future planets.
05:20But the stars themselves did not just disappear.
05:23They collapsed under the effect of their gravity, creating the first black holes.
05:28However, black holes are also known to produce unintentional amounts of radiation.
05:34It is therefore possible that they contributed to accelerate the dissipation of the fog.
05:38Ironically, they would have contributed to make the universe shine by sucking in light.
05:43Recent discoveries show that black holes could be much older than we thought.
05:48They probably participated in the formation of new stars and galaxies.
05:53Their mass was millions, if not billions, times that of the Sun.
05:58The James Webb telescope has already discovered a pair of early quasars.
06:03This is how we call the bright centers of galaxies,
06:06powered by supermassive black holes.
06:09They are quite strange.
06:11They merged 900 million years only after the Big Bang.
06:15It could be the oldest and most distant quasar pair ever discovered.
06:20The telescope has also studied what are called cosmic lights.
06:24In scientific language, they are pulsars.
06:27Pulsars are very dense vestiges of massive stars.
06:31They are formed from stars that were once 4 to 8 times larger than our Sun.
06:36One of their most remarkable characteristics is the speed at which they rotate on themselves.
06:42They are among the fastest objects in the universe.
06:45They can make about 700 rotations in a single second.
06:49They owe their name to the fact that they behave like lights,
06:52that is to say that they emit radiating, flickering waves.
06:57These radiation beams travel through the sky,
07:00creating a signal in the form of an impulse that we are able to detect.
07:04A star works essentially as follows.
07:08Nuclear fusion occurs inside its nucleus.
07:11Atoms merge into each other, move at crazy speeds,
07:16and release an incredible amount of energy.
07:19This is why they emit so much light and heat.
07:22Of course, all this pressure is directed outward.
07:26It's a bit like if the star was sweating big drops in an effort to expand.
07:31The more the fusion is important, the more the star becomes powerful.
07:35On the other hand, gravity pulls the star inward,
07:39trying to compress it so that it retains its shape of a small dense ball.
07:43As long as there is a balance, the star continues to live.
07:46But when it ages and exhausts all its nuclear fuel,
07:50it becomes too weak to produce the energy it needs
07:53and can no longer fight gravity.
07:56Then it collapses under its own weight and explodes into a supernova.
08:00All that remains is the heart of the star,
08:03which is now reduced to an incredibly small scale,
08:06including between 19 and 27 km in diameter,
08:10which is about the size of a city.
08:12This dense nucleus is called a neutron star.
08:15The matter contained in a neutron star is so dense
08:19that a single teaspoon would weigh up to 4 billion tons,
08:23which is the equivalent of 10,000 Empire State Buildings.
08:26All this collapse triggers a reaction that spins the neutron star at full speed
08:31and gives birth to a pulsar.
08:33A bit like when an ice skater starts spinning faster
08:37by crossing his arms on his body.
08:39Pulsars are often accompanied by a smaller star.
08:42Not so long ago, astronomers discovered a pulsar
08:46which, for some unknown reason, was surrounded by a large number of energetic materials.
08:51They realized that all this matter was the remains of another, much larger star.
08:56It turns out that the pulsar had slowly destroyed its friend
08:59with its terrible radiation and particles,
09:02until it had practically devoured it.
09:04It's a bit like a black widow devouring her companion.
09:07These systems were therefore called the black widow pulsars.
09:11Anyway, these lights most likely contributed to the radiation process.
09:17A long time ago, they were very energetic stars in small galaxies,
09:22and they emitted enough radiation to transform the primitive universe.
09:27The James Webb telescope's mission is to find other lights
09:31and determine the role they played in the evolution of our universe.