Universe contains ten times more galaxies than previously thought, Hubble team says

Friday, 14 October 2016

Astronomers have revised their estimate of the number of galaxies in the universe

It's a fundamental question.

How many galaxies are there in the universe?

Astronomers using NASA and Hubble telescope data have completed a 'census' of the number of galaxies in the universe and concluded there are at least ten times more galaxies than previously thought.

Astronomers estimate there are two trillion galaxies, ten times more than previously thought.

One of the Hubble telescope's project aims was to peer deep into space in a bid to gauge the size and age of the universe.

A pan in time across the observable universe

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In the 1990s, during the first sweep of deep space by Hubble astronomers, the scientists revealed an estimate of the universe's size, an unimaginably vast space containing between 100 and 200 billion galaxies.

A Hubble image from the universe ''census'', a deep-sky study by several observatories to trace the formation and evolution of galaxies.

These 'deep field images' were the first astronomical insight into the vastness of the universe. Now, using updated data, an international team led by University of Nottingham professor of astrophysics Christopher Conselice have revealed the first estimate was much too low.

Using deep space data, Hubble imagery, and other data from observatories around the world, the team concluded the estimated number of two billion was low. They estimate around 10 per cent of the galaxies in the universe are observable with the current generation of deep space telescopes.

In other words, 90 per cent of the galaxies in the universe cannot be observed using current astronomical technology.

Two trillion galaxies is the new estimate.

Astronomers converted data into images to make measurements of the number of galaxies during different times in the history of the universe. Mathematical modelling allowed estimates of the galaxies that cannot be observed - yet.

The team captured data that allowed observations 13 billion years into the past.

Conselice said the results had far-reaching implications.

'It boggles the mind that over 90 per cent of the galaxies in the universe have yet to be studied. Who knows what interesting properties we will find when we observe these galaxies with the next generation of telescopes.

'This gives us a verification of the so-called top-down formation of structure in the universe,' Conselice explains.

Conselice said the data suggested galaxies were not evenly distributed and there were more galaxies when the universe was younger. It also suggests a significant evolution in galaxies, an evolution in which galaxies merged.

Findings also contribute to the solution of the famous (among astronomers, anyway) Olbers' paradox, which asks why the night sky is dark. If most galaxies are invisible to observers a combination of light properties, an expanding universe, and absorption of light by intergalactic dust and gas, combine to create a mostly dark night sky.

Findings are published in the Astrophysical Journal.