An international team of astronomers, led by Yale University and the University of California, Santa Cruz, sifted through the sands of time to when the universe was only five percent of its present age. The team discovered a remarkably resplendent galaxy more than 13 billion years in the past and determined its exact distance from Earth using the powerful MOSFIRE instrument on the 10-meter Keck I telescope at the W. M. Keck Observatory in Hawaii. These observations confirmed it to be the most distant galaxy ever measured, setting a new record, according to a press release.
The galaxy, EGS-zs8-1, is one of the brightest and most massive objects in the early universe and was originally identified based on its particular colors in images from NASA's Hubble and Spitzer Space Telescopes.
"While we saw the galaxy as it was 13 billion years ago, it had already built more than 15 percent of the mass of our own Milky Way today," said lead author Pascal Oesch of Yale University, according to a press release. "But it had only 670 million years to do so. The universe was still very young then." The new distance measurement also enabled the astronomers to determine that EGS-zs8-1 was still forming stars very rapidly, about 80 times faster than our galaxy today.
Only a handful of galaxies currently have accurate distances measured in this epoch of the universe and none younger than this.
"It appears that the young stars in the early galaxies like EGS-zs8-1 were the main drivers for this transition called reionization," said co-author Rychard Bouwens of Leiden Observatory, according to the press release.
These new Keck Observatory, Hubble, and Spitzer observations together also pose new questions. They confirm that massive galaxies already existed early in the history of the universe, but that their physical properties were very different from galaxies seen around us today. Astronomers now have very strong evidence that the peculiar colors of early galaxies seen in the Spitzer Space Telescope images originate from a very rapid formation of massive, young stars, which interacted with the primordial gas in these galaxies.
Reference:
"A Spectroscopic Redshift Measurement for a Luminous Lyman Break Galaxy at z = 7.730 Using Keck/MOSFIRE," P. A. Oesch et al., 2015, Astrophysical Journal Letters [https://apjl.aas.org, preprint: https://arxiv.org/abs/1502.05399].
