2024-03-22 11:21:06
The Gaia space telescope, which maps the Milky Way, has identified two groups of old stars at the heart of our galaxy that are believed to have been involved in its formation more than 12 billion years ago, AFP reported.
These two “stellar streams” with their swirling motion are similar to the “first building blocks” of the ancient heart of the Milky Way, where the first stars were born before the galaxy grew into its current spiral shape, says Kyati Malhan of the German Max Planck Institute for Astrophysics.
According to the collected data, each of the two star groups has the mass of about 10 million suns.
“For the first time, we have been able to identify fragments of this protogalaxy,” named Shakti and Shiva – after the Hindu gods, “whose union gave rise to the cosmos,” explains the lead author of the study, published in the Astrophysical Journal.
The Gaia space telescope of the European Space Agency (ESA), which has been operating for ten years 1.5 million km from Earth, in 2022 provided a three-dimensional map of the location and movements of more than 1.8 billion stars.
This map allowed the identification of a population of stars called “poor old hearts” because of their age. It is related to low metallicity (a chemical indicator of a star’s age) and their central location.
This is an important step for galactic archaeology, which aims to reconstruct the various eras in the history of the Milky Way “in the same way that archaeologists would reconstruct the history of a city,” according to a press release from the Max Planck Institute for Astrophysics.
Thus, the Milky Way evolution model suggests “an old central city surrounded by newer neighborhoods,” the institute notes.
But “the further back in time and space we go, the more the picture of galactic history blurs,” Kyati Malhan points out.
Therefore, astronomers are studying this core, identified in 2022. They use a sample of six million stars and study their chemical composition and position with the help of artificial intelligence, reports BTA.
In this way, they determined the two “stellar streams” – Shakti and Shiva, formed 12-13 billion years ago, in the early period of the Milky Way.
Surprisingly, their stars have unusually high metallicities for this large age. This is probably a sign that they are descendants of an earlier generation of stars. When they died, they released chemical elements that were the basis of the interstellar gas from which the stars Shakti and Shiva arose.
“One of Gaia’s missions is to shed light on the infancy of our galaxy, and it is already underway,” says Timo Prousti, project scientist at ESA. Even if it is difficult to “discover the original embryo” of the Milky Way, adds Kyati Malhan.