It seems that astronomers in Australia have spotted the oldest stars in our home galaxy Milky Way. According to researchers, the stars found in the bulge of the galaxy suggest that the Milky Way might have been dominated by hypernovas during the early days of its life. For those who don’t know: hypernova is the term used for extremely powerful celestial explosions.
Another significant revelation made by the astronomers is that these newly discovered old stars are extremely poor in metals or elements that are heavier than helium. They are saying that when these stars were destroyed by giant outbursts called supernovas they discharged those metals into the outer space. Also, according to the astronomers, the younger the stars are, the more metal-rich they are.
Findings of previous research indicated that the first stars were formed around 13.6 billion years back i.e. within 200 million years of the occurrence of Big Bang. The formation of those stars, according to researchers, marked the beginning of a phenomenon called “cosmic dawn”.
The astronomers in Australia haven’t yet spotted any first star but have discovered stars that are extremely poor in metals and are possibly the immediate heirs of the first stars. Those old stars have been spotted in the halo or the outer territories of our galaxy Milky Way.
Previous studies suggested that the metal-poor stars are primarily present in the bulges (the central regions) of the galaxies and not in their halos. Here, it must be mentioned that galactic bulges remain filled with dust and gas, the raw materials required for star formation.
Until now, not a single extremely metal-poor star has been spotted in the bulge of the Milky Way. This is partly because the huge distance between the planet Earth and the galaxy’s bulge and. For those who don’t know: our planet is located in the halo of the galaxy; Earth’s view of Milky Way’s bulge gets obscured with plenty of intervening dust.
There’s also another theory explaining why no metal-poor star has been spotted in the Milky Way. A large share of the stars in the bulge of the Milky Way is rich in metal. As the bulge is filled with a lot of dust and gas, the region saw star formation taking place at a great pace.
Then, as the early stars started dying, the surrounding territories of those stars got enriched with heavier elements and finding metal poor stars in the bulge of the Milky Way became extremely difficult.