spaceSpace and Physics

There Are Two Trillion Galaxies In The Visible Universe


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockJan 17 2017, 16:00 UTC

The Good South Field is one of the areas in the sky used by researchers to estimate the number of galaxies. NASA/ESA/HST

UPDATE: The study has now been published in the Astrophysical Journal. Our story previously appeared at this link. You can read it below. 

Brand new research suggests that the universe is actually a lot more crowded than previously thought. There are up to 2 trillion galaxies in the visible universe, more than 10 times previously estimated.


This research was conducted by professor Christopher Conselice of the University of Nottingham and his collaborators at the Leiden Observatory and the University of Edinburgh, and is the culmination of 15 years work. 

The team looked at the density of galaxies at different epochs and discovered that there seemed to be at least 10 times more galaxies in any given volume in the first few billion years than we see today. Most of those galaxies were small, so they are difficult to observe.

“This is very surprising as we know that, over the 13.7 billion years of cosmic evolution since the Big Bang, galaxies have been growing through star formation and mergers with other galaxies,” Conselice said in a statement. “Finding more galaxies in the past implies that significant evolution must have occurred to reduce their number through extensive merging of systems.”


It was previously thought that the observable universe had 100 billion galaxies – an estimate obtained in the 1990s based on the Hubble Deep Field images. But better models and instruments that have been developed over the last 20 years point towards a busier universe.

According to this latest research, which is available online, there could be between 1 and 2 trillion galaxies out there, and we have only seen a small fraction of them. 

“We are missing the vast majority of galaxies because they are very faint and far away. The number of galaxies in the universe is a fundamental question in astronomy, and it boggles the mind that over 90 percent of the galaxies in the cosmos have yet to be studied,” added Conselice. “Who knows what interesting properties we will find when we study these galaxies with the next generation of telescopes?”


This new estimate has important consequences for how galaxies have evolved throughout the ages of the universe. The rate at which galaxies have merged must have been much higher during the first few billion years of the cosmos.

Astronomy is the science of receding horizons. When our instruments improve, we can then look deeper and further away into the universe, and every advancement has shown that the universe is a lot more complex, bigger, and fuller than we previously thought.

spaceSpace and Physics
  • tag
  • galaxies,

  • galaxy evolution,

  • visible universe