We present 4-meter Kitt Peak telescope and 6.5-meter MMT spectrophotometry of the extremely low-metallicity galaxy SBS 0335–052W , the western companion of the blue compact dwarf galaxy SBS 0335–052E .
These observations have been combined with published 10-meter Keck data to derive for the brightest region of SBS 0335–052W an oxygen abundance 12 + log O/H = 7.12 \pm 0.03 .
This makes SBS 0335–052W the lowest metallicity star-forming galaxy known in the local universe .
Using a Monte Carlo technique , we fit the spectral energy distribution of SBS 0335–052W to derive the age of the oldest stars contributing to its optical light .
We find that star formation in SBS 0335–052W began less than 500 Myr ago , making it a likely nearby young dwarf galaxy .