Le télescope spatial James Webb a encore une fois épaté tout le monde en découvrant comment de petites galaxies ont joué un rôle énorme dans la construction de l'univers. Ces petites galaxies, remontant aux tout premiers temps du cosmos, étaient comme des surdouées cosmiques, produisant des étoiles à un rythme effréné. Grâce à sa puissante vision infrarouge, le JWST a révélé ces galaxies anciennes et faibles que nous ne pouvions pas voir auparavant. Il s'avère que leur énergie et leur lumière ont contribué à façonner l'univers, participant à un phénomène appelé réionisation, qui a rendu l'univers clair et étoilé tel que nous le connaissons aujourd'hui. C'est fou de penser que ces minuscules galaxies ont accompli tant de travail dans le grand plan cosmique. En gros, le JWST nous a donné une autre raison de nous enthousiasmer pour l'univers ! Animation créée par Sympa.
----------------------------------------------------------------------------------------
Musique par Epidemic Sound https://www.epidemicsound.com
Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna
----------------------------------------------------------------------------------------
Nos réseaux sociaux :
Facebook: https://www.facebook.com/sympasympacom/
Instagram: https://www.instagram.com/sympa.officiel/
Stock de fichiers (photos, vidéos et autres):
https://www.depositphotos.com
https://www.shutterstock.com
https://www.eastnews.ru
----------------------------------------------------------------------------------------
Si tu en veux encore plus, fais un tour ici:
http://sympa-sympa.com
----------------------------------------------------------------------------------------
Musique par Epidemic Sound https://www.epidemicsound.com
Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna
----------------------------------------------------------------------------------------
Nos réseaux sociaux :
Facebook: https://www.facebook.com/sympasympacom/
Instagram: https://www.instagram.com/sympa.officiel/
Stock de fichiers (photos, vidéos et autres):
https://www.depositphotos.com
https://www.shutterstock.com
https://www.eastnews.ru
----------------------------------------------------------------------------------------
Si tu en veux encore plus, fais un tour ici:
http://sympa-sympa.com
Category
😹
FunTranscript
00:00Bang, or should I say Big Bang, the Big Bang, hmm.
00:07After the Big Bang, the universe looked like a broth of protons, neutrons and electrons.
00:13After starting to cool down, protons and neutrons began to combine,
00:18first forming ionized hydrogen atoms and later helium.
00:22These ionized helium and hydrogen atoms attracted electrons,
00:26transforming them into neutral atoms.
00:28As a result, light was able to move freely for the very first time,
00:32since it was no longer dispersed by free electrons.
00:35What does that mean?
00:37The universe was no longer dark.
00:40However, it took a few hundred million years after the Big Bang
00:46for the first sources of light to begin to appear.
00:49It was at this moment that cosmic darkness really ended.
00:54We do not know for sure what the first light of the universe looked like
00:58or how the first stars were formed.
01:01Fortunately, the James Webb Space Telescope helps us find answers.
01:05How?
01:07Simply because it is an infrared telescope.
01:10Why is it important? Let's try to understand.
01:13Imagine a star.
01:15It is a very, very old star.
01:17Maybe the first.
01:19The light left this star 13.6 billion years ago
01:23and undertook an incredible journey through space and time.
01:26It must reach our telescopes.
01:28When this light reaches us, its color or wavelength turns red.
01:33This is what we call a shift to red.
01:37This shift is due to the fact that, when it comes to very distant objects,
01:41Einstein's Theory of General Relativity comes into play.
01:45According to this theory, the expansion of the universe
01:48also means that the space between objects stretches,
01:51which moves them away from each other.
01:53But that's not all.
01:55Light also stretches,
01:57which moves it to larger wavelengths.
01:59Finally, this light reaches us in the form of infrared.
02:04In other words, the shift to red means that the light emitted at the origin
02:09by the first stars or galaxies in the form of ultraviolet or visible light
02:14is shifted to redder wavelengths
02:17when we see it here and now.
02:22For the most distant objects with a very high shift to red,
02:26this minimum of visible light is displaced in the electromagnetic spectrum
02:30located in the near and medium infrared.
02:33That's why, to see these objects from space,
02:36we need a super-powerful telescope.
02:38The Webb telescope can see up to 100 million or 250 million years after the Big Bang.
02:43Which is incredibly impressive.
02:46By observing the universe in infrared,
02:49the James Webb telescope allows us to see things
02:52that no other telescope has ever shown us before.
02:55The main objective of this incredible device
02:58is to study the formation of galaxies and stars
03:01that appeared in the first moments of the universe.
03:04To go back so far in time,
03:06you have to look further into space.
03:10All this because it takes time for light to travel to us.
03:14As a result, the further we look, the further we go back in time.
03:19To find the first galaxies,
03:21James Webb will make an ultra-deep survey of the universe in the near infrared.
03:26He will then continue with other research methods.
03:30As you remember, at the beginning of the universe,
03:33the gas between the stars and galaxies was opaque
03:36and the energetic light of the stars could not penetrate it.
03:40Then, about a billion years after the Big Bang,
03:43it suddenly became completely transparent.
03:46Why?
03:47The James Webb telescope may have found the answer.
03:51At one point, the stars of the first galaxies emitted enough light
03:56to ionize and heat the gas that surrounded them.
03:59This allowed to clear sight for hundreds of millions of years.
04:03The most recent knowledge of scientists
04:06dates back to a period called the ionization era.
04:10At that time, the universe underwent spectacular changes.
04:15After the Big Bang, the gases of the universe were incredibly hot and dense.
04:20Hundreds of millions of years have passed,
04:23and the gas has cooled.
04:25Then something amazing happened.
04:28It's as if the universe had pressed the repeat button.
04:32The gas has become ionized and hot again.
04:35This phenomenon could be due to the formation of the first stars.
04:39Then, millions of years later,
04:42this mixture has become transparent.
04:45For a long time, researchers have hoped to find concrete proof of these changes.
04:50Today, the telescope teaches us that these transparent regions
04:53are located around galaxies.
04:55Astronomers have seen these galaxies re-ionize the gas that surrounds them.
05:00Even better, they have managed to measure the size of these transparent regions.
05:05And they are gigantic compared to the galaxies themselves.
05:09Imagine a golf course.
05:11Now imagine a small weight floating inside.
05:15You got it.
05:17And guess what?
05:19These tiny galaxies were at the origin of the entire ionization process,
05:24releasing huge regions of space around them.
05:27These transparent bubbles continued to grow until they merged
05:31and made the entire universe transparent.
05:34The research team chose to target an earlier period at the end of the ionization era.
05:39At that time, the universe was not quite opaque,
05:42but not quite clear either.
05:44It was a patchwork of regions where the gas was in different states.
05:48To discover this amusing fact,
05:50astronomers oriented the James Webb telescope towards a quasar,
05:54an incredibly bright space object.
05:56It acted like a gigantic flashlight,
05:59moving towards us through different gas regions.
06:02Its light was either absorbed by the quasi-opaque areas,
06:05or freely crossed the areas where the gas was transparent.
06:10Scientists then used Webb to examine the galaxies in this region of space.
06:16They discovered that these galaxies were generally surrounded by transparent regions
06:20with a radius of about 2 million light years.
06:24For comparison, the area released by the galaxies
06:27corresponds approximately to the distance separating our galaxy,
06:30the Milky Way, from our closest neighbor, the Andromeda galaxy.
06:35And the telescope was able to observe these galaxies
06:38releasing the space around them.
06:40It was the end of the ionization era.
06:43Until then, no one knew what had caused this process.
06:47The team plans to dive into the research of other galaxies
06:50in five additional areas.
06:53The results obtained by the Webb telescope in the first area
06:56were extremely clear.
06:59While astronomers expected to identify
07:01a few dozen galaxies existing at the time of the reionization,
07:06they found 117.
07:10Let's now talk a little about the main hero of today's video,
07:13the James Webb Space Telescope.
07:16It is an absolutely amazing instrument,
07:19100 times more powerful than the Hubble Space Telescope.
07:22And it has observed places
07:24located at 13.4 billion light years.
07:29To say that the James Webb Space Telescope is a bit expensive
07:31is an euphemism.
07:33While originally, the cost of the telescope was estimated
07:35between 1 and 3.5 billion dollars,
07:39the entire development process cost about 10 billion dollars.
07:43For comparison, the construction and launch of the Hubble Space Telescope
07:47cost NASA 4.7 billion dollars.
07:51And it took another 1 billion dollars to put it into orbit.
07:56Although the James Webb Space Telescope is three-story high
07:59and as large as a tennis court,
08:01its mirrors are the lightest telescope mirrors of all time.
08:05During the manufacturing process,
08:07their weight was reduced by 92%.
08:12When you look at them,
08:13the telescope mirrors seem to be made of gold.
08:17In reality, they are made of beryllium.
08:19It is a steel, light and fragile gray metal.
08:23A layer of gold is applied on each mirror, it is true.
08:26But they cannot be made entirely of gold,
08:29because this precious material tends to dilate and contract,
08:33even in case of low temperature variations.
08:37Thus, the total amount of gold contained in the James Webb Space Telescope
08:42is less than 60 grams,
08:44or a piece of gold the size of a golf ball.
08:47And the gold plates that cover the mirror
08:49have a thickness of less than 1000 atoms.
08:52As far as the telescope's capabilities are concerned,
08:54it would be able to clearly see an American penny
08:57at a distance of 38 km
08:59and a football ball at a distance of 547 km.
09:04The James Webb Space Telescope side cools by itself
09:07and its temperature does not exceed minus 223 degrees Celsius.
09:12It is quite cold to make liquid nitrogen.
09:15A huge five-layer solar shield surrounds the telescope
09:18and reflects the sunlight as much as possible,
09:21allowing the telescope to remain cold.