Science Focus
original post »A surprisingly normal galaxy has been discovered in the very early Universe, providing new information on the beginnings of star formation. The galaxy, A1689-zD1, is one of the oldest and most distant ever discovered. It dates to the epoch of re-ionization, a period in the Universe’s history when the first stars formed beginning about 560 million years after the Big Bang. The galaxy itself is visible as it was about 700 million years into the Universe’s history, or about five percent of its 13.8-billion-year lifespan.
The observation was done using the Very Large Array’s X-Shooter instrument along with the Atacama Large Millimeter/submillimeter Array (ALMA), and it relied on gravitational lensing. The galaxy’s image was magnified over nine times by the galaxy cluster Abell 1689 which lies between zD1 and us—the cluster’s gravity acts as a lens, making the galaxy detectable. Without the magnification, it would have been too dim to observe.
“After confirming the galaxy’s distance using the VLT, we realized it had previously been observed with ALMA,” said Darach Watson, the paper's lead author from the Dark Cosmology Center at the University of Copenhagen. "We didn’t expect to find much, but I can tell you we were all quite excited when we realized that not only had ALMA observed it, but that there was a clear detection. One of the main goals of the ALMA Observatory was to find galaxies in the early Universe from their cold gas and dust emissions—and here we had it!”
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