A group of Spanish astronomers, reviewing the data collected as part of the review of the sky, Sloan Digital Sky Survey hit an object that seemed to have very few metallic elements. Further observations explained this - J0815 + 4729, because this star received the designation, is one of the first to form in the Milky Way after the Big Bang.
The Spaniards directed an interesting star with a mass of about 70% of the mass of the Sun, William Herschel telescopes and Gran Telescopio Canarias, using the spectrographs on them to analyze the spectrum of light coming from J0815 + 4729 to Earth.
These observations have shown that on this celestial body there is a million times less iron and calcium than on the Sun, which indicates the advanced age of the star. At the same time, a lot of coal was seen on it (there is more of it than on the Sun), which goes beyond the age of J0815 + 4729, because "excess" coal had to be created in the first generation of stars that had a huge mass, but also existed very briefly and were very poor in metals, because they did not manage to synthesise them before they exploded as supernovae.
Thus, it means that most likely J0815 + 4729 formed when the Milky Way itself formed, about 13.5 billion years ago, making it one of the first stars in our galaxy.