00:00Ah, hang on to your long view, space rat.
00:04The scientists have made an amazing discovery.
00:07They discovered the ancient heart of our galaxy, the Milky Way.
00:11But what is this ancient heart, and what does it tell us about the history of our galaxy?
00:16Let's see it together.
00:17Is that all?
00:18Yes, yes. Thank you, Captain Jack.
00:20At your service.
00:21Ah!
00:22And yes, what do you want?
00:23He's a space pirate.
00:25The Milky Way is not just a chocolate bar.
00:28It is above all a majestic spiral galaxy that houses billions of stars, planets and other celestial objects.
00:34And it extends over an impressive distance of about 100,000 light-years.
00:39The Milky Way has a characteristic shape, with a central bulb from which spiral arms start.
00:45These arms, comparable to space suburbs, are areas where the stars are more dispersed and the neighborhood more peaceful.
00:52Constituted of gas, dust and stars, they move in harmony, forming a circular pattern around the galactic center.
01:00Among these spiral arms are huge expanses of interstellar space.
01:05These regions, although essentially empty, are home to fine nebulae of gas and dust, as well as captivating spectacles,
01:13such as vast areas of star formation or nebulae with brilliant colors.
01:19The Milky Way is also surrounded by a vast halo of black matter,
01:23a mysterious and invisible substance whose gravitational effects we only perceive.
01:28This halo plays an essential role in maintaining the cohesion of the galaxy and spreading far beyond the visible regions.
01:35And finally, here is the center of the Milky Way, where an intense activity is concentrated.
01:41We find a supermassive black hole, whose mass is about 4 million times greater than that of our sun, Sagittarius A.
01:49This black hole generates phenomena among the most energetic in the galaxy, such as the emission of powerful energy jets.
01:56You probably remember the first picture of a black hole to have gone around the web?
02:01It was Sagittarius A that we managed to immortalize thanks to its proximity to Earth.
02:07All in all, the center of the Milky Way is full of closely clustered stars, forming a particularly dense cluster.
02:14This is precisely where astronomers have recently made an extraordinary discovery.
02:19The heart of our galaxy has been identified.
02:22And what a heart! It is a real fossil.
02:25And a little respect for the elders.
02:28A team of scientific emirates has created a cluster of 18,000 stars, which appeared shortly after the Big Bang.
02:34These ancient stars constituted the primitive nucleus of the Milky Way.
02:38They date from a time when our galaxy was only a collection of proto-galaxies,
02:42uniting progressively to give birth to a larger and more complex structure.
02:47Researchers have nicknamed this cluster the poor old heart of the Milky Way.
02:52Incredible, isn't it?
02:54These stars, over 12.5 billion years old, may only represent 0.2% of the total mass of our galaxy.
03:03But their importance is inestimable.
03:06They constitute the founding bricks that shaped the nucleus around which all the other stars and planets took shape.
03:13But how did these stars become the heart of the galaxy?
03:16How were they formed?
03:18And how did we discover them?
03:20To answer these questions, we must go back in time, to an infinitely distant past.
03:27It was once, nearly 14 billion years ago, the Big Bang.
03:31It was at this moment that our universe was born.
03:34In its first moments, it was of an unimaginable heat.
03:38Then, by cooling down little by little, small pockets of gas began to regroup under the effect of gravity, giving birth to the first galaxies.
03:47The Milky Way is one of these galaxies.
03:49It also began in the form of a modest concentration of gas and dust.
03:55Then, over time, it began to structure.
03:59The first stars, called proto-stars, appeared within the clouds, and their gravity attracted more matter.
04:06This process, spanning millions of years, finally gave birth to the Milky Way.
04:12But to explore more deeply the history of our galaxy, it is necessary to locate these proto-stars, a task that is complex.
04:21It is by analyzing the data from the Gaia mission of the European Space Agency, using a neural network, that researchers were able to identify this ancient core.
04:30The Gaia telescope, a space observatory launched in 2013 by the European Space Agency,
04:36has the mission to map the position and movements of more than one billion stars within our galaxy.
04:42One billion stars!
04:44A colossal task, comparable to counting each grain of sand on a beach.
04:49But Gaia is perfectly up to this challenge.
04:52And how does it work?
04:54The telescope is equipped with two sophisticated cameras that simultaneously photograph the sky.
04:59Their power is such that they can detect stars a million times less luminous than those visible to the naked eye.
05:06By taking multiple clichés of each star, Gaia allows us to follow their movements with remarkable precision.
05:14The data collected by Gaia gives astronomers a better understanding of the structure and history of the Milky Way.
05:21It reveals unprecedented information about stars, such as their age, temperature or chemical composition.
05:28In addition, Gaia contributes to the research of exoplanets, these bodies that gravitate around stars located outside our solar system.
05:37As part of this research, astronomers used Gaia and the most precise 3D map of the Milky Way ever made.
05:45To identify the primordial group, they had to analyze nearly two million stars.
05:50One of the methods to estimate the age of stars is to observe their luminosity and temperature,
05:56thus studying a short phase of their evolution, known as a sub-giant.
06:02But imagine to see located, within the immense center of the Milky Way, a tiny group of stars over 12.5 billion years old.
06:10It's like looking for a needle in a haystack.
06:13Fortunately, researchers had a size advantage, metals.
06:18In the primitive universe, the cores of the first stars were so hot and dense that they were able to fuse atoms,
06:25giving birth to heavier elements, called astronomy metals.
06:30However, these metals do not necessarily correspond to the materials we call in everyday life.
06:37The more massive a star is, the more it produces metals during its existence.
06:42When the first stars reached the end of their lives, they exploded by dispersing these metals.
06:48These then mingled with the surrounding gas and contributed to the formation of the next generations of stars.
06:54Over time, as the universe aged, new generations of stars followed, each containing more metals than the previous one.
07:03Do you see where this is going?
07:05The older a star is, the less it contains metals.
07:09This meant that it was time to turn to a real galactic archeology.
07:13The team formed the IA to identify the oldest and richest stars in metals.
07:20And it took up the challenge.
07:22It spotted a huge pile of stars, all located less than 30,000 light-years from the center of the Milky Way.
07:29Then, astronomers distinguished the stars that made up the ancient core of those from a dwarf galaxy.
07:36In the end, only the original stars around which the Milky Way had grown remained.
07:42This discovery is truly fascinating.
07:44It highlights the remains of the first stages of the history of the Milky Way.
07:48The simulations of its formation proved to be of great precision.
07:52The old stars were exactly where they had been predicted.
07:56Imagine, stars that remember the universe from its beginnings are still today at the heart of our galaxy.
08:04Isn't it extraordinary?
08:06But why is it so important?
08:08By studying these stars, scientists have made remarkable discoveries.
08:12They have confirmed that the core of the Milky Way was initially stationary, and only began to rotate as it grew.
08:19This means that the Milky Way was formed thanks to the fusion of 3 or 4 proto-galaxies,
08:24these stars constituting its very first core.
08:27But even after billions of years and numerous fusions, the heart of the Milky Way has remained intact.
08:33Like an oasis protected within the cosmic tumult.
08:37The Milky Way is a vast and complex structure, full of mysteries and wonders yet to be discovered.
08:44It is a true splendor of the universe, and we have the chance to inhabit it.
08:48But exploration does not stop there.
08:50Researchers want to learn more and more about the formation of our galaxy,
08:54and plan to study these ancient stars with increased precision.
08:59Who knows what revelations could emerge?
09:01Perhaps they will discover the types of supernovae responsible for the elements we know today.
Comments