Related papers: The extremely low metallicity star SDSS J102915+17…

The relative importance of metals and dust grains in the formation of the first low-mass stars has been a subject of debate. The recently discovered Galactic halo star SDSS J102915+172927 (Caffau et al. 2011) has a mass less than 0.8 Msun…

The Gaia Data Release 2 provides a parallax of 0.734+/-0.073 mas for SDSS J102915+172927, currently the most metal-poor known object. This parallax implies that it is dwarf star, ruling out the scenario that it is a subgiant. The subgiant…

Context: The small- to intermediate-mass ($M <0.8 M_\odot$), most metal-poor stars that formed in the infancy of the Universe are still shining today in the sky. They are very rare, but their discovery and investigation brings new knowledge…

Context: The discovery and chemical analysis of extremely metal-poor stars permit a better understanding of the star formation of the first generation of stars and of the Universe emerging from the Big Bang. aims: We report the study of a…

We report the discovery of SMSS J160540.18-144323.1, a new ultra-metal poor halo star discovered with the SkyMapper telescope. We measure [Fe/H] = -6.2 +- 0.2 (1D LTE), the lowest ever detected abundance of iron in a star. The star is…

Using the Large Binocular Telescope (LBT)/Multi-Object Dual Spectrograph (MODS), we have obtained optical spectroscopy of one of the most metal-poor dwarf star-forming galaxies (SFG) in the local Universe, J2229+2725. This galaxy with a…

Dust grains in low-metallicity star-forming regions may be responsible for the formation of the first low-mass stars. The minimal conditions to activate dust-induced fragmentation require the gas to be pre-enriched above a critical…

Only a handful of stars have been identified with an iron abundance [Fe/H]<-5, and only one at [Fe/H]<-7. These stars have very large carbon-to-iron ratios, with A(C)~7.0, most likely due to fallback in core-collapse supernovae, which makes…

The formation of stars is a key process in the early universe with far reaching consequences for further cosmic evolution. While stars forming from truly primordial gas are thought to be considerably more massive than our Sun, stars in the…

We present an analysis of high-resolution Keck/HIRES spectroscopic observations of J0815+4729, an extremely carbon-enhanced, iron-poor dwarf star. These high-quality data allow us to derive a metallicity of [Fe/H]$=-5.49{\pm}0.14$ from the…

We aim to reveal the nature of the Sloan Digital Sky Survey (SDSS) stars: SDSSJ100921.40+375233.9, SDSSJ015717.04+135535.9, and SDSSJ171422.43+283657.2, showing apparently high NUV excesses for their g-z colors, as expected for extremely…

We report the discovery of the carbon-rich ultra metal-poor unevolved star J0815+4729. This dwarf star was selected from SDSS/BOSS as a metal-poor candidate and follow-up spectroscopic observations at medium-resolution were obtained with…

Understanding the formation of the extremely metal poor star SDSS-J102915+172927 is of fundamental importance to improve our knowledge on the transition between the first and second generation of stars in the Universe. In this paper, we…

We discuss the serendipitous discovery of an extremely metal poor galaxy, SDSS 0809+1729, classified as a star in the Sloan Digital Sky Survey (SDSS). The galaxy has a redshift z = 0.0441 and a B-band absolute magnitude M_B = -17.1. With a…

We report on the chemical composition of the very metal-poor ([Fe/H]=-2.9) star LAMOST J1645+4357 that is identified to be a red giant having peculiar abundance ratios by Li et al. (2022). The standard abundance analysis is carried out for…

We report the discovery of the most metal-poor dwarf star-forming galaxy (SFG) known to date, J0811+4730. This galaxy, at a redshift z=0.04444, has a Sloan Digital Sky Survey (SDSS) g-band absolute magnitude M_g = -15.41 mag. It was…

The first stars formed out of pristine gas, causing them to be so massive that none are expected to have survived until today. If their direct descendants were sufficiently low-mass stars, such stars could exist today and would be…

We have derived elemental abundances of a remarkable star, HD 179821, with unusual composition (e.g. [Na/Fe]=1.0$\pm$0.2 dex) and extra-ordinary spectral characteristics. Its metallicity at [Fe/H]=0.4 dex places it among the most metal-rich…

We describe the discovery of HE 1327-2326, a dwarf or subgiant with [Fe/H]}=-5.4. The star was found in a sample of bright metal-poor stars selected from the Hamburg/ESO survey. Its abundance pattern is characterized by very high C and N…

The most metal-poor stars in the Milky Way witnessed the early phases of formation of the Galaxy, and have chemical compositions that are close to the pristine mixture from Big Bang nucleosynthesis, polluted by one or few supernovae. Only…