The universe suddenly looks a lot more crowded, thanks to a deep-sky census assembled from surveys taken by NASA’s Hubble Space Telescope and other observatories.
Based on the observations, scientists make a surprising conclusion that there are at least 10 times more galaxies in the observable universe than previously thought. The finding will soon be published in The Astrophysical Journal.
Researchers from University of Nottingham led the data analysis. They found that 10 times as many galaxies were packed into a given volume of space in the early universe than found today.
Most of these galaxies were relatively small and faint, with masses similar to those of the satellite galaxies surrounding the Milky Way.
As they merged to form larger galaxies the population density of galaxies in space dwindled. This means that galaxies are not evenly distributed throughout the universe’s history.
Researchers suggest that the results are powerful evidence that a significant galaxy evolution has taken place throughout the universe’s history.
The revolution dramatically reduced the number of galaxies through mergers between them, and hence reduces their total number.
Researchers reached this conclusion using deep-space images from Hubble and the already published data from other teams.
They converted the images into 3-D to make accurate measurements of the number of galaxies at different epochs in the universe’s history.
In addition, they used new mathematical models, which allowed them to infer the existence of galaxies that the current generation of telescopes cannot observe.
This led to the surprising conclusion that in order for the numbers of galaxies to add up, there must be a further 90 percent of galaxies in the observable universe that are too faint and too far away to be seen with present-day telescopes.
In the near future, the James Webb Space Telescope will be able to study these ultra-faint galaxies.
News source: The Space Telescope Science Institute.
Figure legend: This Knowridge.com image is credited to NASA, ESA/Hubble.