A small galaxy in the young universe turned out to be a youthful version of the Milky Way.

For the first time, astronomers have studied a young, forming galaxy of relatively small mass just 615 million years after the Big Bang. This galaxy has a mass similar to that of the Milky Way in its early stages. Thanks to gravitational lensing, scientists were even able to observe clusters of stars within this young galaxy.

https://naked-science.ru/article/astronomy/ancient-lowmass-galaxy2024-12-12 10:01:29

Giant galaxies like the Milky Way gradually gained mass through mergers and the accretion of smaller galaxies and star clusters. To understand what they looked like during the earliest stages of formation, astronomers are peering into the young Universe. This task is challenging because the early versions of the Milky Way were likely small—at least 10,000 times less massive. Here, gravitational lensing comes to the scientists' aid.

Massive cosmic bodies act as giant lenses, bending the light that passes through them. One such cosmic gravitational lens is the massive galaxy cluster MACS 1423. We see it as it was when the Universe was already 8.3 billion years old, but its mass distorts and "magnifies" the light from much more distant objects. Among these is the galaxy Firefly Sparkle and its "companions" from a time when the Universe was only 615 million years old.

The authors of a new study, published in the journal Nature, examined the distorted light of Firefly Sparkle using data from the James Webb Space Telescope. Thanks to lensing, the researchers identified 10 star clusters within Firefly Sparkle. Eight of these clusters are located near the center of the galaxy, with the farthest being 4,570 light-years away from the center (1.4 kiloparsecs).

The clusters vary in mass, ranging from hundreds of thousands to a million solar masses. Together, they account for only 49-57% of the mass of the Firefly Sparkle galaxy. According to the authors of the new study, the total mass of the galaxy is about 10 million solar masses. This makes it one of the least massive objects discovered in the young Universe.

Given the mass of the clusters and their high surface stellar density, new stars are actively forming within them. Predicting their future in the Firefly Sparkle galaxy is difficult. They could either merge into its structure or survive to the present as globular clusters.

“Although it is impossible to determine the fate of Firefly and its companions based on observational data, studying such potential progenitors of the Milky Way may provide insights into how it formed,” explained astronomer Brian Welch, who was not involved in the new research.

Based on the structure of Firefly Sparkle, galaxies like the Milky Way could indeed have begun their growth from small groups of dense star clusters.