“If we understand correctly, there could be low mass stars with a composition exclusively from the Big Bang,” says astrophysicist Kevin Schlaufman of Johns Hopkins University. "Although we have not found such an object in our galaxy, it may exist." Recently it became known that astronomers have discovered one of the oldest stars in the Universe, the body of which is almost entirely made up of materials erupted in the Big Bang.
The discovery of this star, almost 13.5 billion years old, means that there may be other stars with low mass and low metal content, relics of the Big Bang - perhaps the very first stars in the universe were just that.
The newly discovered star is very unusual because unlike other stars with extremely low metal content, this one is part of the "thin disk" of the Milky Way - the part of our galaxy, which also contains our sun. And because this star is so old, scientists believe our galactic neighbors may be at least 3 billion older than previously thought. The scientists' findings were published in The Astrophysical Journal.
The star is a child of the Big Bang
The first stars in the universe after the Big Bang were composed entirely of elements such as hydrogen, helium, and some lithium. These stars then produced elements heavier than helium in their cores and filled the universe with them, exploding in supernovae.
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The next generation of stars formed from clouds of material dotted with these metals and incorporated them into their composition. The metal content, or metallicity, in the stars of the universe increased with the repetition of the cycle of birth and death of stars.
The extremely low metallicity of the newly discovered star indicates that there may be only one generation in the cosmic family tree separating us from the Big Bang. In fact, this is a new record holder among the stars with the lowest content of heavy metals - there are as many of them as there is in the planet Mercury. For comparison, our Sun has passed through thousands of generations in this tree and has a heavy metal content equal to that of fourteen Jupiters.
Astronomers have discovered about 30 ancient "ultra-poor metal" stars with the approximate mass of the Sun. The star, discovered by Schlaufman and his team, has a mass of only 14% solar.
This star is part of a system of two stars orbiting a common center. Astronomers discovered this tiny, almost invisible "minor" star after another group of astronomers discovered a brighter "major" star. That team measured the composition of the main star by studying the optical spectrum of its light in high resolution. The presence or absence of dark bands in a star's spectrum can reveal the elements it contains, such as carbon, oxygen, hydrogen, iron, and everything else. In this case, the star had extremely low metallicity. Before that, astronomers also identified unusual behavior of this stellar system, which indicates the presence of a neutron star or black hole. Schlaufman and his team refuted this, but in the process they discovered a tiny companion to the bright star.
The existence of a small companion turned out to be a big discovery. Schlaufman's team was able to deduce its mass by studying the light "wiggle" of the star due to the gravitational pull of the younger star.
Since the 1990s, scientists began to believe that in the earliest stages of the existence of the universe, only massive stars could form - and they could not be observed in any way, because they quickly burned their fuel and died.
But as astronomical simulations became more sophisticated, it became clear that in certain situations, a star from this time period with a particularly low mass could still exist, even more than 13 billion years after the Big Bang. Unlike huge stars, low-mass stars can live for a very long time. It is believed that red dwarf stars can live for trillions of years.
Ilya Khel