  Deep images and near-IR spectra of galaxies in the field of the lensing
cluster SMACS J0723.3-7327 were recently taken in the Early Release
Observations program of JWST. Among these, two NIRSpec spectra of galaxies at
$z=7.7$ and one at $z=8.5$ were obtained, revealing for the first time
rest-frame optical emission line spectra of galaxies in the epoch of
reionization, including the detection of the important[OIII]4363 auroral line
(see JWST PR 2022-035). We present an analysis of the emission line properties
of these galaxies, finding that these galaxies have a high excitation (as
indicated by high ratios of [OIII]/[OII], [NeIII]/[OII]), strong
[OIII]4363/H$\gamma$, high equivalent widths, and other properties which are
typical of low-metallicity star-forming galaxies. Using the direct method we
determine oxygen abundances of $12+\log(O/H)=7.9$ in two $z=7.7$ galaxies, and
a lower metallicity of $12+\log(O/H)\approx 7.4-7.5$ in the $z=8.5$ galaxy
using different strong line methods. More accurate metallicity determinations
will require better data. With stellar masses estimated from SED fits, we find
that the three galaxies lie close to or below the $z \sim 2$ mass-metallicity
relation. Overall, these first galaxy spectra at $z \sim 8$ show a strong
resemblance of the emission lines properties of galaxies in the epoch of
reionization with those of relatively rare local analogues previously studied
from the SDSS. Clearly, the first JWST observations demonstrate already the
incredible power of spectroscopy to reveal properties of galaxies in the early
Universe.
