Astronomers using the Hubble Space Telescope have discovered the most distant,
and therefore the youngest,
object ever observed. The galaxy existed when the universe was only 5% of its present age (redshift 6.68). Stretched by the expansion of the universe,
the wavelength of its light is shifted to the red. This redshift is a measure of age. The previous record holder was 1% older.
The galaxy emits strongly at ultraviolet wavelengths,
indicating a high star
formation rate.
This suggests that early galaxies had much greater star formation rates than galaxies today.
Information can also be gleaned about the
intergalactic medium.
Absorption of the
blue light by intergalactic hydrogen along the
line of sight is nearly 100% much more than light from galaxies slightly closer to home.
This might be because at early epochs the
intergalactic medium was mainly neutral hydrogen,
which later became ionized over a relatively short period when active galaxies started pumping out radiation.
The HST imaging spectrograph is currently a unique tool for discovering faint objects. These new results augur well for observations at the European Southern Observatory’s VLT (see picture of the month),
which will have even greater sensitivity than the HST. A systematic study of very distant galaxies will provide new information on the origin and formation of galaxies essential for cosmological theories.
