J0023+0307: A Mega Metal-Poor Dwarf Star from SDSS/BOSS
David S. Aguado et al 2018 ApJL 854 L34
The primitive star SDSS J0023+0307 has an upper limit [Fe/H] < −6.6, making it one of the two most iron-poor stars known. It is further missing the usual carbon enhancement found in other hyper-metal-poor stars.