Galaxies are considered to be alive or dead depending on how fast they can form star clusters. Young galaxy light is very bright and fast in forming star clusters. But older, bigger, galaxies tend to scatter reddish, dimmer, and then die.
Even so, galaxies that have died can sometimes come back to life. This phenomenon occurs when the galaxy is able to pick up various objects or materials around it. The Milky Way galaxy, where the earth is located, is believed to be one of the galaxies that once died and came back to life.
At least that’s what Masafumi Noguchi from Tohoku University, Japan believed. He and his team conducted a study and found that the Milky Way galaxy once died. The findings were published in the journal Nature. Noguchi focused on observing the chemical composition of stars in the Milky Way galaxy.
According to Noguchi’s calculations, the stars around the sun formed in two different generations. The time interval in the formation between generations is about 5 billion years. There is no means or mechanism by which this mismatch can be established without its profound effect.
Noguchi’s model predicts that star clusters originally formed when cold, intergalactic gas flowed into the young Milky Way. The first generation of these star clusters ended in massive explosions called supernovae, which had two consequences.
First, supernovae produced heavy metal elements which then spread far and wide. This event enriches interstellar gas and changes its chemical composition.
The second consequence is heat. Supernovae create powerful electric waves that raise the temperature of the gases that make up star clusters. Due to the extremely hot temperatures, stars need cold gas for initial formation. If the gas is not cold, star clusters will be difficult to form.
Noguchi highlighted how different types of supernovae release different amounts of different chemical elements. Those from short-lived stars, known as type II supernovae, are rich in alpha elements, such as oxygen, magnesium, and silicon, and occur rapidly. This explains why the older generation was rich in these elements.
Then a void star cluster formation was formed. Finally, a longer-lived supernova, called type I, exploded and released large amounts of iron. The second generation of these star clusters contains more iron. Our sun is among these stars.
The idea that there were two distinct periods in the formation of these star clusters could explain the existence of larger galaxies. It will be interesting to look at the theory of this phenomenon and apply it to medium-sized galaxies, such as the Milky Way.
LIVESCIENCE | OUTERPLACES | WORD ATMAKUSUMA
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