Galaxies such as the Milky Way are believed to have formed through a series of mergers, absorbing small galaxies and star clusters, and possessing these outer stars. In some cases, the mergers were so new that we can still identify the former independent body as a group of stars orbiting the Milky Way. But over time, interactions with other stars in the Milky Way slowly disrupt the structures that make up the cluster. p>
So it is surprising that researchers have found what appear to be the remains of some of the oldest stars around. This finding is consistent with the "growth through integration" model of galaxy building, but leaves the question of how the clusters will remain intact as long as they persist.
Gaia Data Mining
Milky Way. Gaia imaged nearly a billion masses dozens of times, which is enough to estimate its location and motion around the core of the Milky Way. This map helped scientists determine the structures of our galaxy based on the fact that there are groups of stars that are not only physically close to each other, but all move in the same direction. p>
Mining process. Gaia data is very useful for these types of structures as there is a software algorithm called STREAMFINDER that detects them. This program led to the discovery of C-19 stellar streams, a group of stars moving together in the Milky Way's halo. p> Advertising
It is part of one group to check its age. clusters often consist of stars of the same age. One Way to determine if stars are forming at the same time is to look at the content of heavier elements. There were a few elements heavier than helium that were formed during the Big Bang, so most of the heavier elements in existence now came from earlier stars. The later a star formed in the history of the universe, the more likely the heavier elements were present in that star. It's a metal, but that probably confuses most non-astronomers, so we avoid it. can be measured. It belongs to the C-19 stream. With one exception, they were all quite similar, indicating that the actual residual turbulent current is a mass. But the results also contained a surprise: a very small amount of heavy elements. p>
Ancient History h2>
The usual Way to record heavy elements is by the ratio of iron (which only forms. Late in life (a massive star) to hydrogen. Hydrogen has always been the most abundant element in The universe, while iron levels rose slowly over time. So the higher the iron-to-hydrogen ratio, the newly formed star.
In the case of C-19, this ratio was very low. So low that C-19 stars formed. 3 billion years after the Big Bang, or when the universe was only about a quarter of its current age. It may have formed a little earlier.Advertising
In the Milky Way, several hundred stars have been identified at lower levels of similar heavy elements.But no star cluster has been seen in which every star has such a low level.In fact, prior to this discovery, the Milky Way's clusters were thought to contain a layer of heavy elements—all of which have higher levels than we see in C. -19. Despite the fact that based on the distribution of known groups, we would expect to have about five groups with a similar heavy element level e to C-19 level.
Indicates that there are no other groups. Most early clusters like this have already been so disrupted that they have disappeared into the background of the Milky Way's stars. This begs the question: Why didn't C-19 do this? This is particularly unexpected, given that orbit around the galactic core takes it deep into the Milky Way. p>
One possibility might explain this. That is, the cluster first entered the Milky Way as part of a dwarf galaxy and was swallowed up. The structure of a dwarf galaxy can provide a certain degree of protection until it is disrupted and its stars are scattered throughout the Milky Way. And if this is true, then the cluster that formed C-19 contained a significant portion of the stars in the dwarf galaxy at that time. p>
No matter how it ends. To be clear, the presence of the C-19 stream tells us something about the history of the universe. The researchers concluded: "The presence of C-19 proves that globular clusters must have formed in the lowest mineral environments, because the first galactic structures were collected." Nature, 2022. DOI: 10.1038/s41586-021-04162-2 (about DOI).
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