(ORDO NEWS) — A small number of stars scattered around the center of the Milky Way are remnants of an ancient galactic core when our galaxy was still young.
Using measurements from the most accurate 3D map of the Milky Way galaxy ever compiled, as well as a neural network to study the chemical composition of over 2 million stars.
A team of astronomers has identified 18,000 stars from our galaxy’s infancy, when it was just a compact collection of protogalaxies gathered together to dream about more important things.
Hints about this stellar population have been revealed in previous studies.
“But our results,” writes a team led by astronomer Hans-Walter Rix of the Max Planck Institute. for astronomy, “majorly add to the existing picture by showing that there is indeed a closely related in situ ‘iceberg’ whose tops have been previously recognized.”
13 billion years of history of the Milky Way. The path is a gigantic delightful puzzle to be reconstructed from the state of ga. weaker today.
The population of stars can be related based on common features such as their movement and their chemical composition, a property known as metallicity. This is where the ESA Gaia space observatory comes to the rescue.
The satellite has been orbiting the Earth around the Sun for many years, carefully tracking the stars and measuring their three-dimensional position and movement within the galaxy. .
In addition, Gaia makes measurements that allow us to estimate the metallicity of stars.
Metallicity can bind stars together, since stars with similar compositions could have been born in the same place at the same time. But it can also roughly tell us how old a star is, because some elements simply didn’t exist in the universe until the stars that created them appeared.
Immediately after the Big Bang 13.8 billion years ago. , there was not a wide variety of elements. The primordial universe was mostly hydrogen, with a little helium, and nothing else.
As the first stars formed from clumps of this medium, their hot, dense cores began to slam atoms together to form heavier elements: hydrogen into helium, helium into carbon, and so on, all the way up to iron for the most massive stars.
Once stars reach the limit of their ability to fuse atomic nuclei, they die, often in a supernova-like process when their fusion products are ejected into space.
Supernova energy explosions also produce heavier metals such as gold, silver and uranium. Young stars then absorb these elements as they form.
The later a star forms in the Universe, the more metals it contains. Therefore, higher metallicity means a younger star; and low-metal stars are considered older. But not all stellar orbits are the same as they move around the galactic center.
When you find a group of stars with the same abundance of metals on a similar orbital path, it is reasonable to conclude that this group of stars is a population that has existed together for a very long time, perhaps since its formation.
Ricks and his colleagues used the Gaia data to observe red giant stars within a few thousand light-years of the Milky Way.
They identified 2 million stars, the light from which was analyzed by a neural network that could accurately determine metallicity.
And they found a population of stars with similar ages, abundances, and orbits, suggesting they existed before the Milky Way was filled with stars and bloated by collisions with other galaxies, starting about 11 billion years ago.
We know that the oldest stars in the Milky Way date back to before the first major collision with a galaxy called Gaia. -Enceladus, but this population at the galactic center seems to be their entire population.
Ricks called them the “poor old heart” of the Milky Way because they are metal-poor, very old, and can be found in the very heart of the galaxy. The population is, the researchers say, the remnants of protogalaxies.
These clusters of stars that formed in the early universe were not full-fledged galaxies, but their seeds. In the infancy of the Milky Way, three or four of these seeds merged together to form the core of what would become our home galaxy.
The poor old heart stars were not born in these protogalaxies, but there are generations of stars that formed when the stars of the protogalaxy died. Researchers have determined that they are over 12.5 billion years old.
The surprising discovery raises many questions that researchers hope to uncover.
What is the spatial distribution of these stars? Do they have any special abundance ratios that could tell us more about the early conditions of the Milky Way? What can their distribution tell us about the collision history of the Milky Way?
And perhaps most importantly, can they lead us to those stars smaller, dimmer, and harder to find that might have been in the first protogalaxies when they converged in the earliest stages of the formation of the Milky Way?
It may have been old and poor in metals, but the ancient heart of the Milky Way could be extraordinarily rich in answers to questions about our galactic history.
Contact us: [email protected]