The Milky Way galaxy has been our home in the cosmos, but it is not the only galaxy out there. Scientists have always been curious about the number of galaxies in the universe, which plays a significant role in understanding the composition and evolution of our universe. The question of how many galaxies there are in the universe seems deceptively simple, but the answer continues to elude us.
For a long time, it was believed that the Milky Way was the only galaxy in the universe. However, in 1924, Edwin Hubble discovered variable stars in several spiral nebulae, which he used to calculate the distance to these nebulae. His observations showed that these stars were too distant to belong to our Milky Way and instead were members of other galaxies far outside it. Since then, scientists have been trying to determine the number of galaxies in the universe.
In 1995, the Hubble Deep Field was observed, providing the first real deep look into the universe, revealing hundreds of previously unseen galaxies. Further deep observations with Hubble and other instruments followed, detecting even fainter and more distant galaxies. From these observations, astronomers determined that there were a total of 120 billion galaxies within the so-called observable universe, which consists of all objects that can be observed with telescopes like Hubble, those from which light has had time to reach us since the beginning of the universe.
However, a recent analysis of published data from Hubble and other telescopes showed that the previous estimate of the number of galaxies within the observable universe was at least 10 times too low. Scientists believe that some 90% of the galaxies in the universe are too faint and too far away to be observed by the current generation of telescopes. Astronomers can only infer their existence based on models and calculations.
The newly collected data has allowed scientists to look back more than 13 billion years into the past, to the early days of the universe. This look back revealed an early universe in which the density of galaxies was ten times higher than it is today. Most of these galaxies were relatively small and faint, with masses similar to those of the satellite galaxies surrounding the Milky Way. These findings are powerful evidence that galaxies have evolved and grown in numbers throughout the universe’s history, dramatically reducing their total number over time.
With 90% of the galaxies in our universe yet to be observed, there is still much left to explore and discover. The upcoming James Webb Space Telescope promises to offer even more insight into the universe. As we continue to explore the vastness of the universe, we are continually surprised beyond our wildest imagination by nature’s wonders.