Surprise: The Milky Way is not uniform | Uranium

Surprise: The Milky Way is not uniform |  Uranium

Astronomers at the University of Geneva observed the structure of gases Our galaxy In contrast to the existing models, they were shown not to be uniformly mixed.

To better understand the history and evolution of the Milky Way, astronomers study the structure of gases and metals, an important part of our galaxy. There are three main components: the initial gas coming from outside our galaxy, and the interstellar gas inside our galaxy – which is rich in chemical elements – and the dust that results from the condensation of the metals contained in this gas. So far, theoretical models have hypothesized that these three elements are mixed uniformly throughout the Milky Way and are called solar metallicity in a chemical enrichment similar to the Sun’s atmosphere. Now, a team of astronomers at the University of Geneva (UNIGE) has shown that these gases do not mix in the same way as previously thought, which greatly influences the current understanding of the evolution of the galaxy. As a result, simulations of the evolution of the Milky Way need to be modified. The results were published in the journal Nature.

Galaxies It consists of a group of stars, which are formed by the condensation of gas Inter Galaxy Center, Mostly hydrogen and some helium. Unlike gas in galaxies, this gas contains no metals – in astronomy all elements heavier than helium are gaseous atoms but are called “metals”. The galaxies are powered by “virgin” gas, which flows out, reviving them and allowing young stars to form. Analisa D’Sia, professor of astronomy at Unig’s Faculty of Science and the first author of the study, explains. At the same time, stars burn hydrogen throughout their lives and create other elements through nucleosynthesis. When a near-life star explodes, it emits the metals it produces, such as iron, zinc, carbon, and silicon, and introduces these elements into the galaxy’s gas. These atoms can condense into dust, especially in cold, dense parts of the galaxy. Initially, when the Milky Way formed 10 billion years ago, it contained no metals. Then the stars gradually enriched the environment with the metals they produced – The researcher continues. When the amount of metals in this gas reaches the level of the Sun, astronomers talk about solar metal.

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Not a very uniform atmosphere
The Milky Way’s atmosphere is composed of stellar metals and dust particles formed from these metals, as well as galactic gases that regularly flow into the galaxy. “So far, theoretical models have hypothesized that all three elements are homogeneously mixed, reaching the solar system throughout our galaxy, and that there is a slight increase in metal at the center where the stars are most numerous.Patrick Pettigene, a researcher at the Institute of Astrophysics de Paris in Sorbonne, explains. We want to observe this in detail with an ultraviolet spectrograph Using the Hubble Space Telescope

Spectroscopy This allows the light of a star to be divided into specific colors or frequencies, much like a prism or a rainbow. In such distributed light, astronomers are particularly interested in the absorption lines: When we observe a star, the gaseous metals between the star and us absorb a small fraction of the light at a specific frequency, which not only allows us to identify their presence, but also to tell which metal it is and how rich it is. – Continue.

A new method was developed for the observation of the total metal
For 25 hours, a team of scientists used the Hubble i to observe the atmosphere of 25 stars Very Large Telescope (VLT). The problem? Although they contain metals, dust cannot be calculated using these spectrographs. Analisa D’Sia’s team has developed a new monitoring technology. This includes calculating the total composition of gas and dust by simultaneously observing several elements such as iron, zinc, titanium, silicon and oxygen. – Geneva researcher explains. Then we can find the amount of metals contained in the powder and add it to those already measured by the previous observations to get the amount.

Thanks to this dual observation technique, astronomers have found that the Milky Way’s environment is not uniform, and that some of the studied areas reach only 10% of the solar metal. This finding plays an important role in shaping theoretical models for galaxy formation and evolution. Says Jens-Christian Krogager, researcher at UNIGE’s Department of Astronomy. From now on, in order to calculate these metallic changes in different parts of the Milky Way, we will have to increase the resolution and modify the simulations.

These results have a profound effect on our understanding of galaxy evolution, especially our own. Metals play a fundamental role in the formation of stars, cosmic dust, particles, and planets. We know that new stars and planets can form from the gases of very different compositions.

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Agnieszka Novak

More info:
Surprise: The Milky Way is not uniform

Source: UNIGE

In the picture: Artistic vision: Clouds and cosmic “virgin” gas flow into the Milky Way. Source: Dr. Mark A. Garlic

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