Galaxy Scarcity Discovered due to the Early Opaque Universe


Everbody knows that the Universe is kept together by a black cosmic web which nowadays has become almost transparent due to ultraviolet radiation. The web has not the same density over the whole Universe, according to astronomers.

Recent discoveries

A team from the University of Cambridge which was at that time led by Becker discovered that the differences mentioned were so distinct that even the gas was different from place to place.

Becker, an expert on the intergalactic medium, said that “Today, we live in a fairly homogeneous universe and if you look in any direction you find, on average, roughly the same number of galaxies and similar properties for the gas between galaxies, the so-called intergalactic gas. At that early time, however, the gas in deep space looked very different from one region of the universe to another.”

How did they do it?

Aiming to discover the cause of the differences mentioned, the team of University of California astronomers from Santa Barbara, the Riverside,  and Los Angeles campuses used the Subaru telescope, one of the largest ones in the world from the summit of Mauna Kea in Hawaii. They used its powerful camera to look for galaxies 300 million light years in size from a vast region where the intergalactic gas was extremely opaque.

If the cosmic web is more opaque, then there is more gas and more galaxy, but this theory is not accurate. The team discovered that this region included many less galaxies than usual.

“Normally it doesn’t matter how many galaxies are nearby; the ultraviolet light that keeps the gas in deep space transparent often comes from galaxies that are extremely far away. That’s true for most of cosmic history, anyway,” said an assistant professor in the Department of Physics and Astronomy, Becker.


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