An old star has been detected hiding in the Milky Way, almost 35,000 light-years away. The star dubbed SMSS J160540.18-144323.1 possesses the lowest iron levels of any star yet examined in our galaxy. Such a thing means that it’s almost as old as the Universe, and it could belong to the second generation of stars.
The first stars comprised helium and hydrogen and were believed to be very hot, massive, and extremely short-lived. They are now called the Population 3, and until now, astronomers never spotted them.
Ancient Star Challenges Astronomers’ Study
Stars are fueled by nuclear fusion, where the atomic nuclei of lighter elements are fused to develop bigger ones. In less prominent stars, that’s mostly the merging of hydrogen into helium. But, the situation is different for Population 3, because elements such as silicon and iron can be forged. These stars also end their existence in fantastic supernova outbursts, discharging all the elements out into the Universe, and being later absorbed by new stars. How much metal a star holds becomes a strong indicator of when it developed.
Let’s take our host star, for example. The Sun is several, possibly 100 generations apart from the Big Bang, according to its metallicity. But, astronomers discovered other stars in our galaxy that possesses a low metallicity, too, showing an early Universe origin. One such star is SMSS J160540.18-144323.1, which is approximately 11,750 times less metallic than our host star.
“This incredibly anemic star, which likely formed just a few hundred million years after the Big Bang, has iron levels 1.5 million times lower than that of the Sun,” detailed Thomas Nordlander, an astronomer from the ARC Center of Excellence for All Sky Astrophysics in 3 Dimensions.
It’s challenging to examine any Population 3 stars. But, their stories can be unveiled through the stars that appear after. The astronomers think that the star that offered SMSS J160540.18-144323.1 its iron had a low mass for the early Universe, nearly 10 times the weight of the Sun. However, it is immense enough to develop a neutron star; and after a relatively weak supernova, the astronomers think this is what it did.
A supernova outburst can influence a quick neutron-capture phase, dubbed the r-process. Such a phenomenon represents a series of nuclear reactions in which atomic nuclei smash with neutrons to amalgamate elements more substantial than iron. But, there was no proof of these elements in the star, apart from iron. The iron that escaped was part of the development of SMSS J160540.18-144323.1. The astronomers still need time to figure out all these processes.
