Our galaxy was already dying
Scientists astronomers have determined that our galaxy, the Milky Way galaxy, is a natural zombie. Of course she chases after anyone and does not feed on the “brains” of neighboring galaxies, however, she did die once, but the “flame of life” in her depths managed to flare up again.
And on such an unexpected conclusion of Japanese scientists pushed a chemical analysis of the composition of stars belonging to the Milky Way.
All the stars in the Milky Way can be divided into two different groups according to their chemical composition. In the stars of one group, there is an increased concentration of alpha-elements, which include oxygen, magnesium, silicon, sulfur, calcium and titanium. The concentration of alpha-elements in the stars of the second group is much lower, but they contain much more iron in their composition. The existence of two types of stars implies that various processes occur during their formation, but the exact “cosmic mechanism” of this was not clear until recently.
Astronomer Masafumi Noguchi (Masafumi Noguchi) and his colleagues at Tohoku University conducted a computer simulation that spanned up to 10 billion years ago,the results of which provide an answer to the question voiced above. Two types of stars represent two periods of star-forming processes, which were separated by a period of time when the intensity of the process of formation of new stars in our galaxy was practically zero.
The mathematical model originally used by the Japanese was designed to study galaxies whose dimensions exceed those of the Milky Way. The chemical composition of stars depends on the chemical composition of the gas clouds from which they formed. It is known that in the early stages of the existence of the Universe there were very few heavy elements in it, such as metals. These elements were formed later as a result of supernova explosions, which “swept” elements across the expanses of galaxies.
At the first stage of its development, the galaxy attracts and accumulates in its volume cold gas from the surrounding space. And, thanks to the accumulations of this gas, the first generation of stars begins to appear in the galaxy. Stars consisting of light elements are short-lived on cosmic time scales,after about 10 million years, they explode, turning into Type II supernovae and scattering alpha elements arising in their depths around the surrounding space.
Stars that already have a fairly high concentration of alpha elements exist for much longer. But, according to the simulation results, in the Milky Way galaxy something went wrong after 3 billion years after the start of its formation. “As a result of intense supernova explosions, powerful shock waves have arisen, whose energy heated up the high temperature of the cosmic gas cloud,” the researchers write, “And because of this, about 7 billion years ago, new stars practically ceased to form in our galaxy.”
This “pause” lasted about 2 billion years, and its end was marked by a burst of Type Ia supernova explosions, into which stars turn, whose lifetime is at least 1 billion years. It is during these explosions that iron and other metals are formed. When the gas from the last wave of explosions cooled, which happened about 5 billion years ago, the intensity of the star-forming processes took off again,but as a result of these processes, stars began to appear, including a high concentration of iron and other metals. Note that our Sun, which is now about 4.6 billion years old, also belongs to this second generation of stars.
Note that the reliability of the Masafumi Noguchi model has already been tested on the results of research in our neighboring galaxy, the Andromeda galaxy. The processes of star formation in the Andromeda galaxy also went in two stages, separated by an intermediate “dead” stage. And if scientists succeed in obtaining additional confirmations of the Masafumi Noguchi model, this will force them to reconsider some of the existing theories, which exclude the possibility of the existence of a “dead” period in the process of the formation of massive galaxies.