Roughly ninety percent of the Sun comprises two light elements, helium and hydrogen, while the remaining consists of much heavier elements such as iron, carbon, and oxygen. The abundance of heavier elements in stars is known as metallicity, which varies from one star to another.
What is Metallicity?
Stars often consist of hydrogen and helium, where hydrogen particles are turned into helium via nuclear fusion, according to UniverseGuide. This phenomenon takes place during the Main Sequence phase of stars. On the other hand, other elements that exist within the stars make up a small proportion of the star.
There is a relationship between the star's age and the number of metals in it. When we talk about metallicity, metal is considered anything that isn't helium or hydrogen and doesn't have to be metallic elements or those that conduct electricity.
Young stars consist of mostly hydrogen, and only when it reaches sufficient mass will nuclear fusion begin, fusing hydrogen into helium. On the other hand, older stars have less heavy elements existing in them. Nuclear fusion isn't possible in elements heavier than iron because the star dies or explodes. Younger stars such as our Solar System's Sun possibly have been seeded with materials from the previous explosions of dead gigantic stars.
There are three types of metallicity populations. Population I includes stars that have the highest amounts of metallicity and are often youngish stars that can be found mostly in the arms of the Milky Way galaxy. Population II includes stars with lower metallicity because they are older and were created when fewer heavy metals were drifting in space. Lastly, Population III which includes hypothetical stars that were first created when the Universe began its explosions.
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Discovering Low Metallicity Stellar Structures
In a recent discovery, it now turns out that our galaxy, the Milky Way, is hot to a stellar structure that is unique because it is made of stars with extremely low metallicity. These stars are found to have heavy element content 2,500 times lower than the Solar System's Sun and well below any other known stellar structure in the known Universe.
The recent baffling discovery was made by an international team led by researchers from CNRS at the Strasbourg Astronomical Observatory and involved scientists from the Galaxies, Stars, Physics, and Instrumentation Laboratory in Paris. The findings are published in the journal Nature, titled "A stellar stream remnant of a globular cluster below the metallicity floor" detailing how the star group belongs to a stellar structure in the galaxy known as C-19.
The discovery doesn't only challenge current understandings and modeling of stellar groupings formation, which excluded the existence of structures that are solely composed of stitch stars, but it also offers the scientific community a significant set of studies regarding the origin of the first star formations and development of stellar structures in the distant past.
Since heavy elements were originally produced by successive generations of gigantic stars, the low metallicity of the C-19 stars recently discovered shows that they were forms only a brief moment after the Universe' birth.
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