The Milky Way’s thick disk is 2 billion years older than astronomers thought, and likely formed just 800 million years after the Big Bang, according to a new study based on an unusual type of star.
Our galaxy can be divided into two main parts: the thin disk, which contains Solar System Most of what we know as Milky Way; The thicker disc is the rarest, largest and oldest. To reconstruct the history of these components, a team of astronomers from the Max Planck Institute for Astronomy in Heidelberg, Germany analyzed a group of stars In the Milky Way galaxy known as sub-giants.
Sub-stars are stars captured in the short (cosmologically speaking) period between each of them star life and the red giant The stage, in which they expand beyond their original shell.
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Nuclear fusion in the cores of these stars has just stopped, but the stars have not yet turned into red giants. Since the sub-stage in a star’s life lasts only a few million years, astronomers can determine the age of these stars by comparing their chemical composition to computer models of star evolution.
In the new study, scientists determined the ages of 250,000 sub-giants in the Milky Way using data from the European Space Agency (ESA). gaia and the China Multi-Object Fiber Spectroscopic Telescope (LAMOST) in China.
The data revealed that most star formation in the history of the Milky Way occurred in two different waves. The first wave, associated with the thick disk, began only 800 million years after the great explosionAbout 13 billion years ago, but it accelerated 2 billion years later when the nascent Milky Way collided with another galaxy, which astronomers dubbed the Milky Way. Gaia-sausage-enceladusHe told the European Space Agency in SENTENCE.
This collision may have filled the thick disk, as well as the stellar halo that surrounds the entire galaxy with stars. However, it took another 5-6 billion years for the thin disk to appear in the next great wave of star formation, which included Sol.
“Since the discovery of the ancient Gaia-Sausage-Enceladus merger in 2018, astronomers have suspected that the Milky Way did indeed exist…an astronomer at the Max Planck Institute for Astronomy and one of the authors of the paper, He said in a statement Published by the European Space Agency.
studying Published in Nature on March 23.
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