Discovery of ancient stars on the stellar thin disk of the Milky Way

A stunning discovery in regards to the evolution of our galaxy utilizing knowledge from the Gaia mission discovered a lot of historic stars on orbits just like that of our sun. They shaped the Milky Way’s skinny disk lower than 1 billion years after the Large Bang, a number of billion years sooner than beforehand believed.

The Milky Way galaxy has a big halo, a central bulge and bar, a thick disk and a skinny disk. Most stars are positioned within the so-called skinny disk of our Milky Way and observe an organized rotation across the galactic heart. Center-aged stars reminiscent of our 4.6-billion-year-old sun belong to the skinny disk, which was usually thought to have began forming round 8 to 10 billion years in the past.

Understanding how the Milky Way was shaped is a serious objective of galactic archaeology. To attain this, detailed maps of the galaxy that present the ages, chemical compositions, and actions of stars are wanted. These maps, often known as chrono-chemo-kinematical maps, assist to piece collectively the historical past of our galaxy. Creating these detailed maps is difficult as a result of it requires massive datasets of stars with precisely recognized ages.

One frequent method to beat this problem is to review very metal-poor stars, that are outdated, to offer a window into the early Milky Way. Very metal-poor stars are recognized to be outdated as a result of they have been among the many first stars to kind when the universe was nonetheless largely composed of hydrogen and helium, earlier than most of the heavier components have been created and distributed by successive generations of stars.

Utilizing a knowledge set from the European Area Company (ESA) Gaia Mission, a global workforce led by astronomers from the Leibniz Institute for Astrophysics Potsdam (AIP) studied stars within the solar neighborhood, about 3,200 mild years across the sun. They found a stunning variety of very outdated stars in skinny disk orbits; the vast majority of these are older than 10 billion years, a few of them even older than 13 billion years.

These historic stars present a variety of metallic compositions: some are very metal-poor (as anticipated), whereas others have twice the metallic content material of our a lot youthful sun, indicating {that a} fast metallic enrichment passed off within the early phase of the Milky Way’s evolution.

“These historic stars within the disk recommend that the formation of the Milky Way’s skinny disk started a lot sooner than beforehand believed, by about 4–5 billion years,” explains Samir Nepal from AIP and first writer of the research, which has been accepted for publication by Astronomy and Astrophysics and is available on the arXiv preprint server.

“This research additionally highlights that our galaxy had an intense star formation at early epochs resulting in very quick metallic enrichment within the internal areas and the formation of the disk. This discovery aligns the Milky Way’s disk formation timeline with these of high-redshift galaxies noticed by the James Webb Area Telescope (JWST) and Atacama Massive Millimeter Array (ALMA) Radio Telescope.

“It signifies that chilly disks can kind and stabilize very early within the universe’s historical past, offering new insights into the evolution of galaxies.”

“Our research means that the skinny disk of the Milky Way could have shaped a lot sooner than we had thought, and that its formation is strongly associated to the early chemical enrichment of the innermost areas of our galaxy,” explains Cristina Chiappini. “The mixture of knowledge from completely different sources and the appliance of superior machine studying strategies have enabled us to extend the variety of stars with top quality stellar parameters, a key step to guide our workforce to those new insights.”

The outcomes have been made potential by the third knowledge launch of the Gaia mission. The workforce analyzed the stellar parameters of greater than 800,000 stars utilizing a novel machine studying methodology that mixes info from various kinds of knowledge to offer improved stellar parameters with excessive precision. These precise measurements embrace gravity, temperature, metallic content material, distances, kinematics and the age of the celebrities.

Sooner or later, an identical machine studying approach might be used to investigate hundreds of thousands of spectra, collected by the 4MIDABLE-LR survey with the 4-meter Multi-Object Spectroscopic Telescope (4MOST), beginning operations in 2025.