“If we understand correctly, there may be low-mass stars that are composed exclusively of 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 discovered one of the oldest stars in the Universe, whose body is almost entirely composed of materials ejected in the process of the Big Bang.
The discovery of this star by the age of almost 13.5 billion years 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 like 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 – part of our galaxy, in which our Sun is also located. And since this star is so old, scientists believe that our galactic neighbors may be at least 3 billion older than previously thought. The findings of the scientists were published in The Astrophysical Journal.
“This star is probably one of 10 million,” said lead author Schlaufman, an associate professor at the Department of Physics and Astronomy at Johns Hopkins University. “It tells us something very important about the first generations of stars.”
The first stars of the universe after the Big Bang consisted entirely of elements such as hydrogen, helium and a little lithium. Then these stars produced elements heavier than helium in their cores and filled the universe with them, exploding in the form of supernovae.
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 a newly discovered star indicates that there can be only one generation in the cosmic family tree that separates us from the Big Bang. In fact, this is a new record among the stars with the lowest content of heavy metals – there are as many of them in it as 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 the content of fourteen Jupiter.
Astronomers have discovered about 30 ancient “ultra-poor metal” stars with an approximate mass of the Sun. The star discovered by Schlaufman and his team has a mass of just 14% of the sun.
This star is part of a system of two stars orbiting a common center. Astronomers discovered this tiny, almost invisible “secondary” star after another group of astronomers discovered a brighter “main” star. That team measured the composition of the main star, studying the optical spectrum of its light in high resolution. The presence or absence of dark bands in the spectrum of a star can reveal the elements that it contains, such as carbon, oxygen, hydrogen, iron, and everything else. In this case, the star had an extremely low metallicity. Before this, astronomers also identified the unusual behavior of this star system, which indicates the presence of a neutron star or a black hole. Schlaufman and his team disproved this, but in the process they also discovered a tiny companion of a bright star.
The existence of a small companion turned out to be a great discovery. Schlaufman’s team was able to bring out its mass, studying the easy “rocking” of a star, due to the gravitational pull of the youngest star.
Since the 1990s, scientists began to believe that at the earliest stages of the Universe existence, only massive stars could form – and they could not be observed at all, 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 period of time with a particularly low mass can 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.
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