An article about to be published in “The Astrophysical Journal” describes the discovery of the most distant galaxy observed so far. Called GN-z11, it’s about 13.4 billion light years from Earth and that means that we’re seeing the light emitted when the universe was about 400 million years. An international team of astronomers pushed the Hubble Space Telescope to the limit of its possibilities to achieve this result.
In December 2015 the discovery of an ancient galaxy called Tayna was announced, discovered thanks to an effect of a gravitational lens that magnified it, allowing to capture its extremely dim light. GN-z11 is also very old but it’s unusually bright and for this reason, it was possible to observe it among the tens of thousands included in the GOODS North (Great Observatories Origins Deep Survey North) survey.
The characteristics of GN-z11 allowed to use the Hubble Space Telescope’s Wide Field Camera 3 (WFC3) to determine its distance through a spectroscopic analysis carried out splitting its light into its component colors. This measurement is based on the redshift caused by the expansion of the universe.
Astronomers didn’t think that the galaxy GN-z11 was so distant and the spectroscopic analysis of its light revealed that it’s at the limits of the Hubble Space Telescope’s possibilities. This discovery is important because they expected that such distant galaxies could only be observed in a few years by the James Webb Space Telescope. This new generation instrument will find many galaxies from that era and even further back, at the time when the first galaxies formed.
We’re seeing the galaxy GN-z11 when it was very young and its brightness is due to the fact that it’s small, twenty-five times smaller than the Milky Way, but inside it, stars are forming at a rate twenty times higher than that of our galaxy. As in the case of the Tayna galaxy, to evaluate the characteristics of the GN-z11 galaxy observations were carried out with the Spitzer Space Telescope as well.
The discovery of these primordial galaxies helps scientists to achieve a better understanding of how the first galaxies formed when the universe was still very young. The Hubble Space Telescope confirmed it’s an extraordinary instrument and astronomers now know the best ways to use it but more in-depth studies of the GN-z11 galaxy will have to wait until after the launch of the James Webb Space Telescope.
