The stars are the original nuclear fusion reactors. As it evolves, a star permanently merges hydrogen, helium and – if it becomes large enough – more important elements, releasing the energy created in space in the form of light and heat. The first stars, however, were a bit different. Astronomers thought that the first stars of the universe were more “virgins”, which means that they only consisted of the lightest elements.
For years, scientists have thought it was unlikely that such primordial stars still exist – so far. A team of astronomers led by Alexander Ji at the University of Chicago recently revealed that they had spotted a star, SDSS J0715-7334, which seems to have an unprecedented concentration of metals (shortcut of astronomy for elements other than hydrogen and helium). The star seems to be sitting in the halo of the Grand Cloud Magellanic, a dwarf galaxy at around 163,000 light years from the Milky Way. Astronomers have detailed the discovery in an article downloaded from Arxiv, which has not yet been evaluated by peers.
Draw the stellar “genetics”
Carl Sagan is famous for having said that we are made of “star stuff” and at a glance, our evolution and that of the stars seems surprisingly similar. Like us, the stars also belong to distinct “generations” which have slightly different elementary compositions. Scientific consensus has long considered that the first stars, mainly composed of hydrogen and helium, finally exploded in supernovae. These cataclysms have mainly maintained our universe with gas rich in elements that have helped to be born the next generation of stars.
However, astronomers thought that we could still take a look at the direct descendants of the very first stars – a group called population III – looking for low -mass stars with low metallicity.
Abernant “virgin”
The team first detected the SDSS J0715-7334 using data from the Sloan Digital Sky Survey, then used the Magellan telescope in Chile to observe the star more. To be clear, it is not the first astronomers of “virgins” stars – the James Webb space telescope has been particularly able to choose candidates for the stars of the start generation, but SDSS J0715-7334 is distinguished from the others, the researchers noted.
It is “more than ten times poorer in metals” than the discoveries of previous webb, “some of which were allegedly without metal,” wrote astronomers. Not only that, but the star has extremely low carbon levels, which can be a first for similar discoveries. Together, these characteristics make it “the most virgin composition of any known object in the universe”, argued the researchers.
Low carbon levels are particularly interesting, such as “virgins” stars or poor metal stars “previously discovered generally presented high carbon levels. Astronomers thought that relatively heavier elements like carbon allow these stars to cool and not explode.
The lack of carbon on the SDSS J0715-7334 suggests that “different environments in different places in the universe cool their gas differently at first,” said Anna Frebel, MIT astronomer who was not involved in the new newspaper, told New Scientist. “We can ask the question, why do they cool it differently, but I don’t think we have a good answer to that,” she added.
To find out, the search for this type of primordial stars must continue, the researchers said.
