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The galaxy EGS8p7. Credit: NASA/JPL/Hubble

Discovery of farthest known galaxy raises questions about early universe

Using the Keck 1 telescope in Hawaii, astronomers have discovered the most distant galaxy known to man. The galaxy is called EGS8p7 and is over 13.2 billion years old meaning it formed just 600 million years after the big bang, which in cosmic terms is quite short.

The team who discovered it used the redshift method to estimate its distance. As the galaxy moves away from us, as most galaxies are, the red end of the spectrum is stretched. This is known as the Doppler effect. Usually it is quite difficult to detect very distant objects using redshift.

The detection of a certain wavelength of light; however, challenges the current theory of the early universe. The conditions of the universe just after the big bang were much different than today. There were high amounts of free protons, electrons and photons. The free electrons scattered any light that was released so it couldn’t travel at all. Eventually, the universe cooled and the free protons and electrons combined to form hydrogen atoms allowing light to travel through the universe. Then, about 500 million years after the big bang, matter was pulled together by gravity and galaxies formed. Newly formed galaxies reionized the hydrogen clouds back into protons and electrons.

When the Keck 1 Telescope detected EGS8p7, it also detected Lyman-alpha lines, which indicate the presence of hydrogen. This is where the problem arises; these Lyman-alpha lines should have been absorbed by the hydrogen clouds present in the universe before galaxies reionized them. We are seeing EGS8p7 when the universe was full of clouds of hydrogen so at this time, Lyman-alpha lines shouldn’t be detectable.

“If you look at the galaxies in the early universe, there is a lot of neutral hydrogen that is not transparent to this emission. We expect that most of the radiation from this galaxy would be absorbed by the hydrogen in the intervening space. Yet still we see Lyman-alpha from this galaxy.” Said Adi Zitrin who was part of the team conducting the study.

This discovery doesn’t suggest the whole theory of the early universe is wrong but that perhaps some rethinking should be done. One possible reason why the lines were detected is that reionization of clouds may have happened at different rates in different parts of the universe. EGS8p7 may have been more luminous and reionized the clouds much faster than in other areas. Less luminous galaxies would have taken longer to reionize clouds in their locale.

The most exciting part about finding this galaxy is not its age but its distance from Earth. It isn’t much older than the Milky Way, which is also about 13.2 billion years old. Because EGS8p7 is so far away, it allows us to see it at a very young age contrary to our own galaxy which we see as it was very recently. Studying this galaxy could give us more detail as to how the oldest galaxies formed and what conditions were like when they did.

About Harry H

Harry H
Harry is currently studying biology and chemistry in University and hopes to go to grad school for evolutionary biology. He enjoys writing about sciences and sports and is a big fan of hockey and soccer. Some of his other interests are reading and rock climbing. Contact Harry: