2MASS J18082002-5104378 B, an ultra-poor metal star about 1,950 light years away from the Earth, is approximately 13.53 million years ago, becoming one of the oldest stars in our Galaxy Way Milky Way.
The first stars of the Universe after the Big Bang would consist entirely of elements such as hydrogen, helium and small amounts of lithium.
These stars then produced heavier elements than helium in their nuclei and sowed the Universe with them when they exploded as supernovae.
The next generation of stars was formed from material clouds fitted with these metals, incorporating them into their composition.
The metallic content or metallicity of the stars of the Universe increased as the cycle of birth and death continued.
The 2MASS J18082002-5104378 B, also known as Gaia DR2 6702907209758894848 B, is unusual because unlike other stars with very low metal content, it is part of the fine disk & # 39; of the Milky Way: the part of the Galaxy in which our own Sun resides.
"This star is perhaps one in 10 million. She tells us something very important about the first star generations," said lead author, Dr. Kevin Schlaufman, a researcher at Johns Hopkins University.
The extremely low metallicity of 2MASS J18082002-5104378 B indicates that, in a cosmic genealogical tree, it could be as little as a generation eliminated from the Big Bang.
In fact, it is the new record holder of the star with the least complement of heavy elements: it has the same content of elements heavy as the Mercury planet. In contrast, our Sun is generations by that line and has a content of heavy elements equal to 14 Jupiters.
Astronomers have found around 30 stars – ultra-metallic-poor & # 39; old with the approximate mass of our Sun. 2MAS J18082002-5104378 B, however, only 14% is the mass of the Sun.
The star is a small, almost invisibly weak member in the 2MASS binary system J18082002-5104378.
Dr. Schlaufma and colleagues found him after another group of astronomers discovered the "most primary" star more brilliant.
This team, directed by Dr. Jorge Meléndez of the University of São Paulo, measured the primary composition studying a high-resolution optical spectrum of its light.
The presence or absence of dark lines in the spectrum of a star can identify the elements it contains, such as carbon, oxygen, hydrogen, iron and much more. In this case, the star had very low metallicity.
Dr. Meléndez and the authors also identified unusual behavior in the star system that involved the presence of a neutron star or black hole.
Dr Schlaufman's team discovered that it was incorrect, but in doing so they found the much smaller companion of the visible star.
The existence of the smaller companion star turned out to be the great discovery.
Dr. Schlaufman and his colleagues managed to deduce their mass by studying the light "narrow" of the primary star when the gravity of the small star was pulling it.
As recently as the 90s, astronomers believed that only massive stars could form in the early stages of the Universe. But as astronomical simulations became more sophisticated, they began to suggest that, in some situations, there could still be a star of this period of time with a particularly low mass, up to more than 13 billion years ago from the Big Bang.
Unlike the huge stars, people of low mass can live for very long periods. Red dwarfs, for example, with a fraction of the mass of the Sun, are thought to live in billions of years.
The discovery of 2MASS J18082002-5104378 B opens the possibility to observe even older stars.
"If our inference is correct, then there may be low-mass stars that have an exclusive composition of the Big Bang result. Although we still do not find such an object in our Galaxy, it may exist," said Dr Schlaufman.
A report about the discovery is published in the Astrophysical journal (preprint of arXiv.org).
Kevin C. Schlaufman et al. 2018. An Ultra Metal star-poor near the hydrogen combustion limit. ApJ 867, 98; DOI: 10.3847 / 1538-4357 / aadd97