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Astronomers Discover the Heart of the Milky Way Galaxy

Astronomers from the European Space Agency have discovered the ancient heart of the Milky Way.

Thanks to ESA’s Gaia telescope, astronomers have discovered the ancient heart of the Milky Way, a cluster of stars that is much older than the very galaxy we call home for harboring our own Solar System.

Using measurements from the most accurate three-dimensional map of the galaxy ever compiled, as well as an intelligent learning neural network, astronomers at the Max Planck Institute for Astronomy were able to probe the chemical compositions of more than 2 million stars and among them located the heart of the Milky Way.

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The composition of stars tells us a lot about the complex puzzle of understanding our galaxy, which apparently was formed 13 billion years ago. Especially when it comes to metal compositions, a feature is known as metallicity, scientists can understand at what point in galactic history stars formed.

The European Space Agency’s Gaia satellite telescope, which is in orbit, is in charge of measuring the metallicity of stars, among many other things. This is why the team of researchers led by astronomer Hans-Walter Rix of the Max Planck Institute for Astronomy, took on the task of finding the oldest stars that would be the heart of the Milky Way.

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The Less Metal, the Older

Just after the Big Bang, 13.8 billion years ago, there was no great diversity of elements available as there is today. There was hardly any hydrogen and helium that formed the first primitive stars in the cosmos. But as time went on, the dense cores of the primordial stars were heated to great temperatures and staggering pressures, which began to smash atoms together to form new elements.

Hydrogen was transformed into helium, helium into carbon, and so on, until iron, which is the main component of the cores of the most massive stars. Once these stars reached the end of their lives, they exploded as supernovae, which are characterized by spewing the products of their nuclear fusion into space. Supernovae, in turn, generate a large amount of heavier metals, and thus we arrive at the composition of gold, silver, and other heavy metals such as uranium.

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It is thanks to this chronology in the behavior of metals that astronomers can determine the age of the stars, because the greater the composition of metals, the more likely it is a young star. The fewer metals they have, the older they are.

But when it comes to the Universe, everything must be studied as if it were a puzzle and not isolated facts, so metallicity is not only useful to determine stellar ages, but also to find groups of stars that were born during the same epoch.

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The Old Heart of the Milky Way

The Gaia and neural network data helped Rix and his colleagues find a population of 18,000 stars with similar metallicities, meaning that they share similar ages and orbits. According to the data from the telescope, the group of stars would have lived in the Milky Way about 12.5 billion years ago.

Rix has named these stars the ‘poor old heart’ of the Milky Way because they are metal-poor, very old, and located in the very heart of the galaxy. They are so old that they may contain the remains of much older protogalaxies and have been around since before the Milky Way was filled with stars and swollen by collisions with other galaxies.

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Researchers have said that the Milky Way’s old heart, the very old cluster of stars, could shed light on the origins of our galaxy and its early stages of formation, which are still not very clear to astronomers.

Story originally published in Spanish in Ecoosfera

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