Universe contains at least two trillion galaxies

Our universe contains at least two trillion galaxies – 10 times more than we thought.

Astronomers led by Christopher Conselice at the University of Nottingham in the UK converted “pencil beam” images of deep space stretching some 13 billion light-years into 3-D maps, allowing them to calculate the density of galaxies in that volume. 

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This painstaking work along with mathematical models to infer galaxies as-yet unobservable with current technology was published in The Astrophysical Journal.

One of the most fundamental questions in astronomy is: how many galaxies are in the universe? The landmark Hubble Deep Field, taken in the mid-1990s, gave the first real insight into the universe’s galaxy population. 

Subsequent sensitive observations such as Hubble’s Ultra Deep Field revealed a myriad of faint galaxies. This led to an estimate that the observable universe contained about 100 billion galaxies.

Conselice and colleagues found, not surprisingly, most overlooked galaxies are faint and very far away. 

And when the universe was only a few billion years old, there were 10 times as many galaxies in a given volume of space as there are within a similar volume today.

As they merged to form larger galaxies, the population density in space dwindled. This means that galaxies are not evenly distributed throughout the universe’s history. 

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