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Upper panel: Fit of the effective temperature to the first three Balmer lines (labeled) in the MIKE high-resolution spectrum, compared to models at the preferred Teff = 4850 K. The lines are shown on a velocity scale centred on each line, and have been offset vertically. The grey shaded blocks represent the wavelength ranges used in the χ2 minimisation. Middle panel: Fit of the surface gravity to the WiFeS medium-resolution spectrophotometry, with a zoomed inset showing the Balmer jump region, at the preferred log g = 2.0. Lower panel: Example fits to lines of Fe and Mg in the MIKE high-resolution spectrum. In all panels additional models illustrate the sensitivity, and the legend lists the models as shown from top to bottom. Credit: Nordlander et al., 2019.
An international team of astronomers has detected a new ultra metal-poor star with the lowest ever measured abundance of iron. Designated SMSS J160540.18−144323.1, the newly found object is the most iron-deficient star for which iron has been detected. The finding is presented in a paper published April 16 on the arXiv pre-print repository.
Stars - Objects - Stars - Iron - Abundances
Metal-poor stars are rare objects as only few stars with iron abundances [Fe/H] below –5 have been discovered so far. Currently, SMSS J0313–6708, with metallicity below –7.3, is the most iron-poor star known to date. However, the most iron-poor star where iron has actually been detected is HE 1327−2326 with metallicity at a level of −5.7.
Astronomers are interested in expanding the still short list of metal-poor stars as such objects have the potential to improve our knowledge of the chemical evolution of the universe. The early evolution of the universe is believed to be dependent on the properties of the first generation of metal-free stars.
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