In the mid-1990s, images captured by the Hubble Space Telescope revolutionized our understanding of the cosmos by allowing astronomers to estimate that there were between 100 and 200 billion galaxies in the observable universe. Now, according to Space.com's Hanneke Weitering, these same images, known as the “Hubble Deep Field, ” have been re-analyzed - and have surprised scientists again.

According to Hanneke, an international team of astronomers decided to reevaluate deep-field images in conjunction with other data collected by Hubble himself and other telescopes, and turned it into a detailed three-dimensional map. The new analysis revealed that, in fact, the old estimate of the number of galaxies in the observable universe was well below the real - and that there are 10 to 20 times more galaxies in the cosmos than previously thought!

New census

The discovery came after astronomers converted the data they gathered into 3D images and employed new mathematical models to calculate the existence of galaxies that probably have not yet been "seen" by today's telescopes - because they are not bright enough or too far away. so that equipment can detect them.

Mosaic showing original images of Hubble Deep Field - where each dot represents a galaxy

Astronomers analyzed regions as far as 13 billion light years away, which allowed them to make more accurate measurements of the number of galaxies in different periods of universe history. This is because, in observing such far-flung regions of the cosmos, scientists have actually looked into its past - since light takes a great deal of time to travel such vast distances.

As they explained, 13 billion years ago, in the early days of the universe — that is, a few million years after the Big Bang — there were far more galaxies than today. However, as the cosmos expanded and evolved over time, although new galaxies formed, many galaxies eventually merged into larger ones.

Thus, according to scientists, the first census did not take into account that the distribution of galaxies is not constant throughout the evolution of the universe. Moreover, the fact that telescopes cannot detect the brightness of faint or far-off galaxies does not mean that they do not exist - and all this helps to explain the discrepancy between the previous and the current census.