Immediately after the Big Bang the universe consisted of hydrogen,
helium and a small amount of lithium. All other elements were formed
later in the course of various processes of stellar evolution. Due to
this fact, we can determine the age of the luminaries. The higher the
metallicity of a star (the percentage of heavy elements), the younger it
is. And vice versa.
During the analysis of the spectra of 2.5 million stars of the Milky
Way, a group of Spanish astronomers drew attention to one very unusual
luminary, known as J0815 + 4729. It is in the halo, at a distance of
7500 light years from the center of the Milky Way. This is a sphere of
spherical shape, extending beyond the visible part of the galaxy.
Basically it consists of rarefied hot gas, stars and dark matter. Mass
J0815 + 4729 is 0.7 solar, the surface temperature is 400 degrees more
than our luminary. The spectroscopic analysis of the star showed that it
has an abnormally low metallicity. In particular, the star contains a
million times less calcium and iron than the sun. And this means that
J0815 + 4729 is one of the oldest stars of the Milky Way, formed shortly
after the death of supermassive stars of the third generation.
Interestingly, despite such a small percentage of iron, J0815 + 4729
contains a fairly large amount of carbon (about 15% of the solar). A
similar feature is characteristic of many low-metal stars. According to
astronomers, this is due to the fact that during the formation of such
luminaries, the main source of the formation of elements heavier than
hydrogen was supernovae type II, which produced a large amount of
carbon, oxygen, silicon, etc.
