Spectroscopic identification of a galaxy at a probable redshift of z = 6.68

The detection and identification of distant galaxies is an important goal of observational cosmology, as such galaxies are seen at a time when the Universe was very young. The development of new techniques and instrumentation permits the search for everfainter galaxies, and so aids attempts to determine when the first stars and galaxies formed. Here we report the identification of a galaxy at a probable redshift of 6.68, the most distant object yet detected. The galaxy's spectrum is characterized by an abrupt discontinuity at a wavelength λ ≃ 9,300 Å, which we interpret as arising from the absorption of light at shorter wavelengths by hydrogen gas along the line of sight (the Lyman-α decrement), and by an emission line at λ ≃ 9,334 Å, which we interpret as the Lyman-α line at a redshift of 6.68. The galaxy is relatively bright: the ultraviolet luminosity density contributed by this one galaxy is almost ten times the value measured at z = 3.