00:00They should not have existed. No one expected to discover them.
00:05Scientists fail to explain their formation.
00:08And yet, it did not prevent the James Webb Space Telescope from identifying them.
00:17These six galaxies, as massive as our Milky Way, are populated with mature red stars.
00:23They are so far from us that they appear as tiny red dots.
00:29Even for this high-end telescope.
00:31Astronomers have analyzed the light emanating from these galaxies and estimated their age.
00:36They would have appeared 500 to 700 million years after the Big Bang.
00:43So far, nothing surprising.
00:45Galaxies so young are not really rare.
00:48Scientists think that the first clusters of stars could emerge shortly after the universe left what is called the Dark Age.
00:59Which corresponds to the first 400 million years of its existence.
01:02At that time, only a thick fog of hydrogen atoms filled the cosmos.
01:09What is particularly strange about these galaxies is their unmeasured size and the advanced age of the stars that make them up.
01:16This contradicts current theories about the appearance and evolution of the universe in its early years.
01:22In addition, these observations differ from those made previously by the Hubble Space Telescope, the less advanced predecessor of James Webb.
01:33So, according to scientists, what are these first galaxies supposed to look like?
01:38The answer is simple, young and small.
01:41Indeed, until now, most of the galaxies of the primitive universe discovered are babies of space, small and blue.
01:49They seemed to have emerged only recently from the primordial cosmic soup and were still forming their first stars and other ensembles.
01:57Most of the young stars are actually blue.
02:00As they age, they acquire a more reddish hue after having burned their stellar fuel and cooled down.
02:06This is why astronomers did not expect to discover red, aging stars in ancient galaxies that the James Webb telescope was designed to observe.
02:17Another unexpected surprise would have been to discover galaxies more massive than a billion suns.
02:23And yet, this is indeed what happened.
02:27The recently discovered galaxies are almost as immense as the Milky Way, with respective masses only 2 to 4 times less.
02:35The most surprising thing is that these galaxies were already so vast when the universe had only reached 3% of its current age.
02:43But before astronomers revise their theories to explain how galaxies so immense could form so quickly after the Big Bang,
02:52it is crucial to verify that these observations are not due to another space phenomenon.
02:58Even in this specific case, most alternative theories require the introduction of entirely new concepts.
03:05One of these theories proposes that stars in the primitive universe emit light in an unusual way.
03:12Since astronomers were not aware of this, this possibility was not included in their model.
03:18Or, what we know about the formation of stars could be inapplicable to the primitive universe.
03:25If one of these theories turned out to be accurate, it would completely revolutionize our understanding of stellar formation.
03:35Now let's move on to the device that allowed astronomers to discover these extraordinary galaxies.
03:41The James Webb Space Telescope is a technological marvel about 100 times more powerful than the Hubble Space Telescope.
03:48And Hubble, in its time, was able to observe objects located 13.4 billion light years away.
03:56The James Webb Space Telescope is also very expensive, and it is an euphemism.
04:01Although its initial cost was estimated at between $1 and $3.5 billion,
04:06the complete development will ultimately have cost the bagatelle $10 billion.
04:10In comparison, the construction and launch of the Hubble Space Telescope, with Eve, cost $4.7 billion at NASA,
04:18with Inve, $1.1 billion more required to repair it in orbit.
04:24Although the James Webb Space Telescope is the height of a three-story building and the size of a tennis court,
04:30these mirrors are the lightest among all the great telescopes ever built.
04:35When they were designed, their weight was reduced by 92%.
04:43At first glance, the mirrors of the telescope seem to be made of gold.
04:47But they are actually made of beryllium, a light metal.
04:51Although a gold coating is applied to each mirror, they cannot be entirely made of it,
04:57because this precious material expands and contracts with temperature variations.
05:05In fact, the total amount of gold used in the James Webb Space Telescope is less than 57 grams,
05:11which represents a piece of gold the size of a golf ball.
05:15The layers of gold covering the mirrors are only 1,000 atoms thick.
05:20As for the telescope's capacity, it can clearly distinguish a 1-centimeter piece at a distance of 38 kilometers
05:27and a 550-kilometer football ball.
05:35The James Webb Space Telescope side maintains an exceptionally low temperature.
05:41The James Webb Space Telescope side maintains a temperature not exceeding 223 degrees Celsius,
05:48in other words, cold enough to liquefy nitrogen.
05:52A giant five-layer solar shield surrounds the telescope and reflects the solar light,
05:58thus keeping the device at a low temperature.
06:04It is thought that James Webb will be able to detect water on distant exoplanets.
06:08For a long time, astronomers have been discovering new planets orbiting around their own stars,
06:13observing the slight variations in luminosity that occur when planets pass in front of their stars.
06:19In addition, it is possible to analyze the spectral signature of light to determine the chemical composition of a planet.
06:27The strongest and most readable signatures appear in the infrared spectrum.
06:33And guess what?
06:35The James Webb Space Telescope is equipped with high-tech infrared instruments.
06:39These can help scientists discover new planets and even identify the presence of water on them.
06:47The telescope was launched near the equator because the Earth's rotation there is slightly faster,
06:52thus giving an additional impulse to the rocket.
06:55Once the James Webb Space Telescope runs out of fuel,
06:59it will continue to gravitate around the Sun indefinitely.
07:02Although the device was not designed to be maintained or improved,
07:06it could potentially be refueled by robots, which would extend its lifespan.
07:13At first, astronomers at CITESOMF were convinced that it would take time for James Webb to discover anything exciting.
07:19They thought that the first galaxies to be observed would be so dark and small
07:24that the telescope would only discover a few rare distant candidates.
07:29However, the results exceeded all expectations.
07:32As soon as the first images were broadcast, scientists began to discover countless galaxies,
07:38vast, bright, and remarkably old.
07:41The competition between research groups to identify new clusters beating all records still persists today.
07:49An astronomer even claimed that the scientific community was on edge
07:53because no one had really anticipated such spectacular results.
07:58One of the main objectives of the Webb Space Telescope
08:01is to observe the light of the very first stars and galaxies in the universe.
08:05Alas, the farther an object is, the faster it moves away from us,
08:10and the more the light it emits must travel from a distance,
08:13thus stretching towards the infrared of the spectrum,
08:16a phenomenon known under the name of redshift in astronomy.
08:20However, thanks to its high-end infrared instruments,
08:24James Webb can reveal worlds that were previously invisible.
08:28Thanks to this telescope, we were able to observe incredibly distant galaxies,
08:33formed about 13.8 billion years ago.
08:37This means that the light detected by James Webb took more than 13 billion years to reach Earth.
08:43Can you imagine what that means?
08:46Among these galaxies, one stands out particularly.
08:49It seems to be the oldest ever discovered by astronomers.
08:54It is called Galas Zezam 13 and dates back only 300 million years after the Big Bang.
09:01The oldest galaxy previously identified by scientists, GN Zaonze,
09:07was discovered by the Hubble Space Telescope and dates back 400 million years after the Big Bang.
09:14During this barely explored period, the very first galaxies and stars began to emerge.
09:22But how exactly did this process take place?
09:25No one knows for sure, at least for now.
09:29This phenomenon could depend on unknown physical laws,
09:32including the influence of dark matter and dark energy,
09:36or on some interactions that have yet to be studied between gas, dust and stellar light.
09:42The fact is that, thanks to Webb telescopes,
09:45scientists can now test their theories on events that occurred after the universe was born.
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