New ultra-poor metal star discovered

An international team of astronomers has detected a new ultra-poor metal star with the lowest iron abundance ever measured. Designated SMSS J160540.18-144323.1, the new object found is the most iron-deficient star for which iron has been detected. The conclusion is presented in an article published April 16 on the arXiv pre-print repository.

Poor metal stars are rare because only a few iron-rich stars [Fe/H] less than -5 have been discovered so far. Currently, SMSS J0313-6708, with a metallicity lower than -7.3, is the iron poorest star known to date. However, the lowest iron star where iron was detected is HE 1327-2326 with a metallicity at a level of -5.7.

Astronomers are interested in expanding the still short list of metal-poor stars, as such objects can potentially improve our understanding of the chemical evolution of the universe. It is believed that the early evolution of the universe depends on the properties of the first generation of metal-free stars.

A group of astronomers led by Thomas Nordlander of the Australian National University searched for a new addition to the list of very low-grade stars, using the SkyMapper telescope in Australia and spectrographs of 39, other ground telescopes. The observations revealed that the SMSS star J160540.18-144323.1 (SMSS 1605-1443), located in the halo of the Milky Way, probably some 36 000 light-years away, contains a very low abundance of iron. .

"We report the discovery of SMSS J160540.18-144323.1, a new ultra-metal poor halo star discovered with the SkyMapper telescope," the researchers wrote.

Research has shown that SMSS 1605-1443 is a red giant-branched star with an effective temperature of about 4,850 K and a remarkably low abundance of heavier elements, including a very low abundance of iron at – 6.2.

While the chemical abundance of other elements of SMSS 1605-1443 has proven compatible with the alpha-enhanced chemical composition typical of halo stars, the object under study shows a sharp increase in carbon . According to the study, this suggests an enrichment of a supernova mixing and folding population III (the first generation of metal-free stars).

"The stars of population III exploding supernova fold could explain both the sharp increase in carbon and the apparent lack of improvement in the abundance of neutron and Z-capture elements. odd, "the astronomers noted.

In conclusion, the researchers pointed out that the metallicity of the SMSS 1605-1443 is the lowest among the stars for which iron has been detected, that it has an overabundance of carbon and that it does not show strong increase or strong tendency to abundance of heavier elements than carbon. Subsequent observations of this star, studying higher quality spectra, could allow a more detailed chemical analysis, which could result in more clues about the nature of its Population III progenitor star.

© 2019 Science X Network