Pourquoi Uranus et Neptune Ont-Elles Un Jour Échangé Leurs Places

Sympa

Uranus et Neptune ont peut-être échangé leurs places il y a longtemps ! Les scientifiques pensent que, dans les premiers jours de notre système solaire, ces deux géants glacés ont inversé leurs orbites. Cette théorie provient de simulations informatiques qui montrent qu'un échange rendrait l'arrangement actuel des planètes plus logique. C'est assez fou de penser à ces énormes planètes participant à un jeu cosmique de chaises musicales. L'espace est plein de surprises, n'est-ce pas ?  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

Transcript

00:00It could well be that we have fallen into the sea of all water reserves, and it floats in space.

00:07It has been hiding under our nose for at least 12 billion years.

00:11As for its size, it is difficult to imagine.

00:15140,000 billion times larger than all the oceans of our planet combined.

00:21This cosmic aquatic world is orbiting a large black hole called Quasar,

00:28located 12 billion light years away.

00:30Quasars are supermassive black holes that emit colossal amounts of radiation.

00:36It is estimated that this one is 20 billion times heavier than our sun,

00:40and that it carries an energy capable of illuminating 1,000 billion.

00:45In our Milky Way, we are used to seeing water in the form of ice.

00:50The water reserve we are talking about here seems to be in the form of steam.

00:54The important thing in this discovery is that there could be water everywhere in the universe.

00:59All you have to do is know where to look.

01:02You may be surprised to learn that all the stars are not hot to the touch.

01:06Until now, we believed that all the stars were as bright as our sun,

01:11fireballs ready to melt everything in their path.

01:15But there are colder ones, the brown dwarfs.

01:18Their particularity lies in the fact that they are too small to carry out the nuclear fusion

01:23that allows the stars, like our sun, to shine.

01:26They do not emit much light or heat, which makes them difficult to see.

01:31These brown dwarfs are divided into different categories.

01:34The coldest Hygia-type stars have a surface temperature lower than that of a cup of tea.

01:40If you could touch one, you would only feel a soft heat.

01:45About 4 billion years ago, Uranus apparently exchanged its place with Neptune.

01:51It is difficult to imagine that such large planets could do that.

01:55But this theory could solve the mystery of the formation of our solar system.

02:00We know that rocky planets formed as a result of major collisions.

02:04Take our planet, for example.

02:06About 4 to 6 billion years ago, things were quite shocked around the sun

02:11until the Earth reached its final form.

02:14During this period, a larger collision made enough rocks and gases explode

02:20to give birth to the Moon.

02:22But as for our neighbors in the solar system, Jupiter, Uranus and Neptune,

02:27scientists still have no answer.

02:30According to standard models, it would take an eternity for them to form.

02:34It would exceed the age of the solar system itself.

02:37If this new theory is correct,

02:39then Uranus and Neptune would be born from a dense gas cloud compacted around the sun.

02:44The problem is that for this theory to stand,

02:48these planets must have exchanged their places at some point in history.

02:52Neptune is about 4.5 billion kilometers away,

02:57the largest distance a planet can reach in our solar system.

03:01Uranus is a little closer, at 3 billion kilometers.

03:05This new idea suggests that after their formation,

03:07much closer to the sun than they are today,

03:10their positions have been modified.

03:12This could be due to the passage of many comets for billions of years

03:16that would have slowly moved these giant planets away.

03:19This is not a definitive answer to the question of how they formed.

03:24It is rather a strong intuition supported by many data.

03:28Speaking of strange things found in our universe,

03:32what about this floating spoon that NASA's Curiosity rover photographed on Mars

03:38while the rover was walking on the red planet?

03:41It fell on this strange spoon-shaped rock in the summer of 2015.

03:46The rock has a handle and even projects a shadow on the ground.

03:50It is not an abandoned utensil during a Martian picnic,

03:54but what NASA scientists call a ventifact,

03:58a rock carved by the wind.

04:00This is not the first time that the Martian surface has delighted us with strange wind sculptures.

04:05There was the face on Mars, a rat, and even beignets with jam.

04:12It is possible that diamonds rain on more than 1900 exoplanets.

04:17Scientists have discovered that it is not necessary to have particularly high temperatures

04:22for carbon to turn into diamonds, as it was believed before.

04:27Until recently, we only knew Neptune and Uranus as likely to present such rain.

04:33Astronomers have been interested in this phenomenon for about forty years.

04:38But these planets were difficult to study.

04:41Only the Voyager 2 probe was able to take a look.

04:45However, considerable progress has been made thanks to laboratory simulations.

04:52Neptune and Uranus are ice giants,

04:55because their outer layers are filled with hydrogen, helium, water and ammonia,

05:00what scientists call ice.

05:03Their magnificent blue hue is due to the methane present in their atmosphere.

05:09But diamond rains occur lower, in the depths.

05:13If we could visit them, we would see that under the thick atmosphere,

05:17there are very dense layers of ice.

05:20All this pressure leads to chemical reactions

05:23that can generate diamonds the size of a small city.

05:28We cannot plunge into Neptune or Uranus with a probe looking for diamonds.

05:33Instead, we reproduce these conditions in laboratories

05:37by pressing the matter between diamond clusters

05:40and hitting it with lasers to imitate the extreme environment of these planets.

05:45Thanks to this, scientists have managed to create artificial diamonds.

05:50Understanding how these rocks are formed there

05:53could also explain why Neptune is warmer than it should be,

05:57and why it knows such intense storms.

06:00These diamonds could also allow us to pierce the mystery

06:03of the strange magnetic fields of Uranus and Neptune.

06:07If we compare what is happening on our planet,

06:10we find very different results.

06:12So there may be strange things going on with the magnetism of these planets.

06:16NASA plans to send a new probe to Neptune or Uranus in the next decade.

06:22As the planets will align perfectly in 2030,

06:25the time will be ideal to explore these sparkling worlds up close.

06:32Planet Kepler-78b is another strange cosmic discovery.

06:37This hot world, in fusion,

06:39goes around its star in record time, once every eight and a half hours.

06:44It is only 1.6 million kilometers away.

06:49If we could put our foot on its surface,

06:52we would notice that its sun is 80 times larger

06:55than the star we see every day in our sky.

06:59If we apply what we know so far about the formation of the planets,

07:03this little guy should not even be there.

07:06Specialists still have no idea how it appeared

07:10or where it is.

07:12What we know is that it will soon disappear, in a way.

07:17As it is extremely close to its sun,

07:20this burning planet will collide with it in a few billion years.

07:25It's relatively short on the cosmic level.

07:29What is similar between our planet and Kepler-78b is density.

07:34Of course, it is about 20% larger than Earth

07:38and weighs almost twice as much,

07:40but it has the same solid interior.

07:42It is impossible for it to form closer to its star

07:45and for it to simply move away over time.

07:48It cannot be born much further away and have migrated inwards.

07:52Any movement inwards would have been impossible to stop.

07:56And it would have collided with the star.

07:59This discovery may not be particularly revolutionary,

08:02but there is a good chance that you never thought about it.

08:05There may be space dust in your hair right now.

08:09Every day, piles of materials from space come crashing down on Earth.

08:13Sometimes, these objects are visible,

08:16like when a meteor turns into a meteorite by crashing on the ground.

08:21But most of the time, it's more discreet.

08:23These materials drift through the atmosphere and land

08:26in the form of what we call space dust.

08:29It may not be much,

08:31but it is about 14 tons per day.

08:34This dust contains tiny fragments of rocks and metals

08:37detached from asteroids and comets during major collisions.

08:41These particles are very small.

08:43You wouldn't be able to see them without sophisticated instruments.

08:46But every time you leave your home,

08:48a part of these particles may land in your hair.

08:53NASA Jet Propulsion Laboratory, California Institute of Technology

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