Le centre de la Voie lactée est super brillant parce qu'il est rempli de nombreuses étoiles et d'un trou noir supermassif. Ce trou noir, appelé Sagittarius A*, est des millions de fois plus grand que notre soleil ! Il attire du gaz, de la poussière et même des étoiles, et à mesure qu'ils s'approchent, ils chauffent et brillent, rendant la zone vraiment lumineuse. Il y a aussi un énorme nuage de gaz chaud et des tonnes d'étoiles entassées, ce qui ajoute à la lueur. Certaines étoiles explosent en supernovas, qui sont aussi extrêmement lumineuses. Plongez pour explorer cela et d'autres faits intéressants sur l'espace. Animation créée par Sympa.
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Musique par Epidemic Sound https://www.epidemicsound.com
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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
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Si tu en veux encore plus, fais un tour ici:
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FunTranscript
00:00Is there a gigantic mega sun in the center of our Milky Way?
00:04Scientists have actually believed that for a while, because it is the brightest region of the galaxy.
00:10It contains millions of stars concentrated in a restricted area called the galactic bulb.
00:17The galactic bulb contains a density of stars per light year much higher than that of any other part of the galaxy.
00:24It can be up to 10 million times denser than our sector.
00:27Sometimes, the stars are separated by only 5 light days,
00:31which would correspond to the presence of another star in our solar system,
00:35just beyond Pluto at the spatial scale.
00:38But what explains such a density?
00:41During the formation of galaxies, large amounts of gas and dust
00:45come together under the influence of gravity.
00:48These materials accumulate and eventually form stars.
00:52Gravity and the kinetic moment find a balance,
00:55giving rise to a flat disk structure with a dense and luminous core,
00:59often presenting a bulging shape.
01:01The stars continue their quiet existence,
01:04and when they reach the end of their life cycle,
01:06they collapse under their own weight,
01:08which leads to the formation of a black hole.
01:11Black holes are greedy for everything that surrounds them,
01:14and the more they absorb matter, the more they grow.
01:17And what better place for a cosmic feast than the center of the galaxy,
01:21where matter is gathered in abundance.
01:23When the black hole begins to absorb gas and surrounding dust,
01:27it forms an accretion disk.
01:29As this matter spirals towards the black hole,
01:32it heats up and releases a large amount of energy,
01:35thus making the center of the galaxy even brighter.
01:38This is why we find both supermassive black holes
01:42and galactic bulbs in the center of all galaxies.
01:46The galactic bulb located in the center of the Milky Way
01:49has a slightly elliptical shape.
01:51It is what is called a classic bulb.
01:53The stars in this region differ from our sun.
01:56They move randomly in all directions and all possible planes,
02:01and each has a different speed.
02:03Gravity is therefore chaotic there,
02:05which gives the bulbs an appearance close to a sphere or an ellipse.
02:09Being the first to form,
02:11these areas house some of the oldest stars in our galaxy.
02:15However, there are also stellar formation regions,
02:19populated by young massive stars,
02:21aged less than 100 million years.
02:23As we move away from the center,
02:25the environment becomes more peaceful.
02:28The stars begin to rotate regularly and stabilize.
02:32Currently, the Earth is in one of the spiral arms of the Milky Way,
02:37called the Orion arm,
02:39located at a great distance from the galactic bulb.
02:42In our neighborhood,
02:43the stars are generally separated by 4 or 5 light years.
02:47This implies that most of a galaxy
02:49is actually made up of a black and empty space.
02:53Our black hole is called Sagittarius.
02:56It is huge,
02:58with a mass about 4 million times that of our sun.
03:02Its size is also about 51 million kilometers in diameter,
03:06which is comparable to the distance between Mercury and the sun.
03:10But do not worry,
03:12it does not threaten to swallow the Milky Way or absorb us.
03:15These black holes are actually very small compared to the whole galaxy
03:20and can only consume what is nearby.
03:23Currently, many stars orbit around Sagittarius A.*.
03:28Although it emits a huge amount of energy,
03:31its light is difficult to observe from Earth
03:34without a significant scientific effort.
03:36But why don't we see the center of our own galaxy?
03:40The galactic bulb is so bright
03:42that at 26,000 light years away,
03:44we should see it shine intensely in our sky.
03:48And yet, this is not the case.
03:50The reason is interstellar dust.
03:53There is a large amount of dust between us and the galactic nucleus,
03:57which absorbs most of the visible light.
03:59We can only observe the galactic nucleus
04:02by using other types of light,
04:04such as near infrared or gamma rays.
04:08NASA has images of the nucleus taken in different types of light,
04:12showing how extremely bright the center is
04:15without the dust that obstructs our view.
04:17However, all luminous regions are not hidden by gas and dust.
04:21For example, when we observe dense clusters like Messier 13,
04:25the stars are so close to each other
04:28that they appear like a simple white spot.
04:30Most telescopes cannot distinguish them.
04:33The M32 satellite galaxy,
04:35our neighbor near the Andromeda galaxy,
04:37contains about 84 stars per light year.
04:40Its density is such that even the Hubble Space Telescope
04:43cannot process the stars individually.
04:46To get an idea,
04:47our solar system measures about two light years long.
04:51If we were there,
04:52we could see about 168 stars through the window.
04:56The closest stellar system to us is Alpha Centauri,
04:59located about four light years from the Sun.
05:02If it was only a few light days away,
05:04it would shine much more intensely than the full moon.
05:07Thus, if we managed to survive in extremely dense star regions,
05:12the sky would be completely white all day.
05:15But it is unlikely to be achievable.
05:18As we get closer to the center of the Milky Way,
05:21the chances of finding life become extremely low.
05:24The gravity of the stars is extreme,
05:26with unpredictable movements,
05:28leaving little room for other objects.
05:31On these rare planets,
05:32the radiation of cosmic rays is incredibly high.
05:35Supernova explosions and star collisions nearby become frequent,
05:40and the surrounding gas makes it almost impossible to breathe,
05:43or even have a clear vision.
05:45On the other hand,
05:46as we move away,
05:47the number of stars decreases.
05:49The essential elements of life,
05:50such as carbon,
05:51oxygen,
05:52and iron,
05:53produced by the stars,
05:54also become less numerous.
05:56Too much radiation is harmful,
05:57but too little radiation means
05:59that there is not enough energy to support crucial chemical reactions,
06:03such as photosynthesis.
06:05This is why,
06:06if extraterrestrial life exists,
06:07it would probably be somewhere in the more central regions of galaxies.
06:11But some galaxies must have their sparkle at an active galactic nucleus.
06:15These are extremely energetic regions,
06:18located in the center of certain galaxies.
06:21They shine much more intensely than any imaginable star.
06:25However,
06:26their luminosity manifests itself mainly
06:28in certain parts of the electromagnetic spectrum.
06:31This luminosity does not come from stars,
06:33but from the accretion disk surrounding their supermassive black holes.
06:37As matter slowly falls into a black hole,
06:40it accumulates around it,
06:42and forms a flat disk
06:44of gas,
06:45dust,
06:46and other rotating elements.
06:48Due to the extreme conditions of gravity and friction,
06:51this disk heats up
06:53and begins to emit enormous amounts of energy.
06:56In addition,
06:57this disk rotates at a speed almost equal to that of light.
07:00As a result,
07:01collisions occur constantly
07:03and are of unimaginable power,
07:05releasing even more energy.
07:07Most galaxies do not have an active galactic nucleus,
07:11or Enneag.
07:13Those that do,
07:14like the M87 galaxy in the constellation of the Virgin,
07:17are called active galaxies.
07:19There are also different types of Enneag,
07:22such as the Seyfert galaxies,
07:24the Radio galaxies,
07:26and finally the Quasars,
07:28which are the champions in terms of spatial luminosity.
07:31Imagine objects so brilliant
07:33that they can surpass the luminosity of the entire galaxy to which they belong.
07:37Quasars are a particular type of active galactic nucleus,
07:41the most extreme and brightest form.
07:44They are associated with supermassive black holes,
07:47the largest in our universe.
07:49Quasars are like a combination of several phenomena.
07:52First of all,
07:53they are the brightest accretion disks that can be observed.
07:56Thanks to their huge black holes,
07:58which absorb everything that surrounds them,
08:00they also have remarkable characteristics.
08:03Powerful particles jets
08:05that burst from the black hole's shoulder
08:07at speeds close to that of light.
08:09These jets increase the luminosity of the Quasar,
08:12although they can only be detected in the form of radio waves.
08:15The energy they emit is such
08:17that they can be observed for billions of light years.
08:20However,
08:21the closest Quasar is located at 600 million light years,
08:25which makes its observation impossible with amateur telescopes.
08:29Thus,
08:30when we observe a galaxy through a telescope,
08:33we usually only see the brightest nucleus,
08:36neglecting the external parts.
08:38Alas,
08:39our eyes are simply not made to perceive objects
08:42like galactic active nuclei.
08:44This is why these stars are among the brightest we can see.
08:48But what a stunning spectacle!