Astronomers have discovered an exceedingly odd star that they believe is a stellar fossil, or relic, of one of the universe’s very earliest stars.
AS0039 is a star in the Sculptor dwarf galaxy, approximately 290,000 light-years from the solar system. This stellar remnant contains the lowest concentration of metal, notably iron, of any star recorded beyond the Milky Way. The researchers believe the discovery proves that the relic is a direct descendant of one of the universe’s early stars, which had relatively little metal.
The scientists discovered that the primordial parent star of AS0039 would have been roughly 20 solar masses and would have died in a hypernova a stellar explosion 10 to 100 times more intense than an ordinary supernova.
The finding might disclose fresh information on the universe’s early stars, which have never been directly or indirectly viewed before. AS0039 has such an odd chemical makeup that it allows us to investigate the characteristics of the first stars and, in particular, their stellar mass, according to research by an astronomer at the University of Cambridge in England.
Though all stars are balls of heated gas called plasma, fuelled by the fusion of atoms in the core, they are also incredibly different; they may vary greatly in size and color. However, depending on their chemical makeup, or metallicity, all stars may be divided into three separate groups: Population I, Population II, and Population III.
Population I stars, like the sun and most other stars in the observable universe, have a high metal content, particularly iron, and are rich in comparatively heavy elements such as calcium and magnesium. Population II stars, such as AS0039, are far more uncommon; these metal-poor stars contain only trace quantities of heavy metals. Population III stars, which have never been seen, are almost completely metal-free and contain no heavy elements.
Although no Population III stars have been discovered, astronomers believe that the very first stars born in the cosmos would have been Population III stars. Hydrogen atoms are fused to form helium during nuclear fusion, which produces a massive quantity of energy. Most stars up to 1.4 solar masses gradually deplete their hydrogen fuel, swell to red giants, and then collapse into white dwarfs.
Larger stars, on the other hand, swiftly deplete their hydrogen reserves and begin to fuse helium into carbon, and eventually carbon into iron, the heaviest metal a star can produce. These huge stars eventually get too thick and collapse in on themselves, exploding in a supernova, which not only disperses the star’s materials into the surrounding space but also releases enough energy to generate elements heavier than iron.
New stars are frequently born amid the clouds of gas left behind by previous stars, so as they develop, they absorb some of the metal and heavy elements from the exploding stars that came before them.
The first stars in the cosmos, however, were Population III stars, which originated from pure hydrogen, the first element generated after the Big Bang. Population III stars are defined as the first generation of stars to develop in the cosmos, and as such, they are composed of zero metallicity. Because there had been no supernovae, these original stars lacked heavy metals as well.
When scientists discovered AS0039, they were astounded by how metal-depleted it was, even when compared to comparable Population II stars.