The furthest galaxy is located at the edge of the observable universe

A team of astronomers used the Keck I telescope to measure the distance to an ancient galaxy. They deduce that the target galaxy GN-z11 is not only the oldest but also the most distant.


It is so distant that it defines the very limit of the observable universe itself. The team hopes that this study can shed light on a period in cosmological history when the universe was only a few hundred million years old.


"Based on previous studies, the GN-z11 galaxy appears to be the farthest detectable galaxy from us, at 13.4 billion light-years," University of Tokyo professor Nobunari Kashikawa, lead author of the study, said in a statement. "But measuring and verifying that distance is not an easy task."


Kashikawa and his team measured what is known as the GN-z11 redshift; This refers to the way the light spreads, it gets redder, the more it travels. Certain chemical signatures, called emission lines, print different patterns in light from distant objects. By measuring how widespread these telltale signatures are, astronomers can deduce how far the light must have traveled, thus revealing the distance from the target galaxy.


"We looked at ultraviolet light specifically, since that's the area of the electromagnetic spectrum that we expected to find the redshifted chemical signatures," Kashikawa said. "The Hubble Space Telescope detected the signature multiple times in the GN-z11 spectrum. However, even Hubble cannot resolve the ultraviolet emission lines to the degree we needed. So we turned to a more up-to-date ground-based spectrograph an instrument to measure emission lines, called MOSFIRE, which is mounted on the Keck I telescope in Hawaii. "    


The MOSFIRE captured GN-z11's emission lines in detail, allowing the team to make a much better estimate of its distance than was possible from previous data.    


When working with distances on these scales, it is not sensible to use our familiar units of kilometers or even multiples of them; instead, astronomers use a value known as the redshift number denoted by z. Kashikawa and his team improved the accuracy of the galaxy's z-value known as the redshift number denoted by z. Kashikawa and his team improved the accuracy of the galaxy's z-value by a factor of 100. If subsequent observations can confirm this, astronomers can say with confidence that GN-z11 is the farthest galaxy ever detected in the universe.

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