Use of Data ESA's Gaia mission Astronomers have discovered a number of metal-poor stars that are more than 13 billion years old and in orbits similar to our sun.
Rotational motion of a young (blue) and an older (red) star similar to the Sun (orange). Image credit: NASA / JPL-Caltech / R. Hurt / SSC / Caltech.
“The Milky Way has a large halo, a central bulge and bar, and thick and thin disks,” said Dr Samir Nepal of the Leibniz Institute for Astrophysics Potsdam and his colleagues.
“Most of the stars are found in a thin disk of the so-called Milky Way galaxy, which revolves regularly around the galactic center.”
“Middle-aged stars like our Sun, which is 4.6 billion years old, belong to a thin disk that is generally thought to have begun to form between 8 and 10 billion years ago.”
Astronomers used the new Gaia data set to study stars within about 3,200 light-years of the Sun.
They found a surprisingly large number of very old stars in the thin disk orbit, most of which are over 10 billion years old, with some being over 13 billion years old.
These ancient stars show a wide range of metal compositions: some are very metal-poor (as expected), while others have twice the metal content of the much younger Sun, indicating that rapid metal enrichment occurred early in the evolution of the Milky Way.
“These ancient stars in the disk suggest that the formation of the Milky Way's thin disk began much earlier than previously thought, around 4 to 5 billion years ago,” Dr Nepal said.
“This study also reveals that the Galaxy underwent intense star formation early on, leading to rapid metal enrichment in its inner regions and the formation of a disk.”
“This discovery brings the Milky Way's disk formation timeline into line with that of high-redshift galaxies observed with the NASA/ESA/CSA James Webb Space Telescope and the Atacama Large Millimeter Array (ALMA).”
“This shows that cold disks can form and stabilize very early in the history of the universe, providing new insights into the evolution of galaxies.”
“Our study suggests that the Milky Way's thin disk may have formed much earlier than previously thought and that its formation is closely linked to an early chemical enrichment in the innermost regions of the galaxy,” said Dr Cristina Chiappini, astronomer at the Leibniz Institute for Astrophysics Potsdam.
“The combination of data from different sources and the application of advanced machine learning techniques has allowed us to increase the number of stars with high-quality stellar parameters, which is an important step leading our team to these new insights.”
of paper will be published in journal Astronomy and Astrophysics.
_____
Samir Nepal others2024. Discovery of local counterparts of disk galaxies at z > 4: The oldest thin disk in the Milky Way using Gaia-RVS. A&Ain press; arXiv: 2402.00561
Source: www.sci.news
