  The cluster CL1358+62 displays a prominent red arc in WFPC2 images obtained
with the Hubble Space Telescope. Keck spectra of the arc show Ly alpha emission
at 7204 Angstrom, a continuum drop blueward of the line, and several absorption
lines to the red. We identify the arc as a gravitationally lensed galaxy at a
redshift of z=4.92. It is the highest redshift object currently known. A
gravitational lens model was used to reconstruct images of the high-redshift
galaxy. The reconstructed image is asymmetric, containing a bright knot and a
patch of extended emission 0.4 arcsec from the knot. The effective radius of
the bright knot is 0.022 arcsec or 130 h^-1 pc. The extended patch is partially
resolved into compact regions of star formation. The reconstructed galaxy has
I_AB= 24, giving a bolometric luminosity of about 3e11 Lsun. This can be
produced by a star formation rate of 36 h^-2 Msun /yr (q0=0.5), or by an
instantaneous star burst of 3e8 Msun. The spectral lines show velocity
variations on the order of 300 km/s along the arc. The Si II line is blue
shifted with respect to the Ly alpha emission, and the Ly alpha emission line
is asymmetric with a red tail. These spectral features are naturally explained
by an outflow model, in which the blue side of the Ly alpha line has been
absorbed by outflowing neutral H I. Evidence from other sources indicates that
outflows are common in starburst galaxies at high and low redshift. We have
discovered a companion galaxy with a radial velocity only 450 km/s different
than the arc's. The serendipitous discovery of these two galaxies suggests that
systematic searches may uncover galaxies at even higher redshifts.
