By pushing the NASA/ESA Hubble Space Telescope to its limits astronomers have shattered the cosmic distance record by measuring the distance to the most remote galaxy ever seen in the Universe. This galaxy existed just 400 million years after the Big Bang and provides new insights into the first generation of galaxies. This is the first time that the distance of an object so far away has been measured from its spectrum, which makes the measurement extremely reliable. The results will be published in the Astrophysical Journal.
Using the NASA/ESA Hubble Space Telescope an international team of astronomers has measured the distance to this new galaxy, named GN-z11. Although extremely faint, the galaxy is unusually bright considering its distance from Earth. The distance measurement of GN-z11 provides additional strong evidence that other unusually bright galaxies found in earlier Hubble images are really at extraordinary distances, showing that we are closing in on the first galaxies that formed in the Universe.
Previously, astronomers had estimated GN-z11’s distance by analysing its colour in images taken with both Hubble and the NASA Spitzer Space Telescope. Now, for the first time for a galaxy at such an extreme distance, the team has used Hubble’s Wide Field Camera 3 (WFC3) to precisely measure the distance to GN-z11 spectroscopically by splitting the light into its component colours. ...
<<In Big Bang cosmology, reionization is the process that reionized the matter in the universe after the "dark ages", and is the second of two major phase transitions of gas in the universe. As the majority of baryonic matter is in the form of hydrogen, reionization usually refers to the reionization of hydrogen gas. The primordial helium in the universe experienced the same phase changes, but at different points in the history of the universe, and is usually referred to as helium reionization.
The first phase change of hydrogen in the universe was recombination, which occurred at a redshift z = 1089 (379,000 years after the Big Bang), due to the cooling of the universe to the point where the rate of recombination of electrons and protons to form neutral hydrogen was higher than the reionization rate. The universe was opaque before the recombination, due to the scattering of photons (of all wavelengths) off free electrons (and, to a significantly lesser extent, free protons), but it became increasingly transparent as more electrons and protons combined to form neutral hydrogen atoms. While the electrons of neutral hydrogen can absorb photons of some wavelengths by rising to an excited state, a universe full of neutral hydrogen will be relatively opaque only at those absorbed wavelengths, but transparent throughout most of the spectrum. The Dark Ages of the universe start at that point, because there were no light sources other than the gradually redshifting cosmic background radiation.
The second phase change occurred once objects started to condense in the early universe that were energetic enough to re-ionize neutral hydrogen. As these objects formed and radiated energy, the universe reverted from being neutral, to once again being an ionized plasma. This occurred between 150 million and one billion years after the Big Bang (at a redshift 6 < z < 20). At that time, however, matter had been diffused by the expansion of the universe, and the scattering interactions of photons and electrons were much less frequent than before electron-proton recombination. Thus, a universe full of low density ionized hydrogen will remain transparent, as is the case today.>>
This graphic shows a timeline of the universe, stretching from the present day (left) all the way back to the big bang (right). The position of the record-breaking galaxy GN-z11 is shown not far from where the first stars began to form. The previous record holder's position is also identified.
Credit: NASA, ESA, P. Oesch (Yale), G. Brammer (STScI),
P. van Dokkum (Yale), and G. Illingworth (UCSC)
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