Scientists have long believed that there were approximately 200 billion galaxies in the known universe, but as it turns out, they were wrong – new surveys compiled using the Hubble Space Telescope have revealed that there are at least 10 times more than previously thought!
According to CNN and the Los Angeles Times, researchers from the University of Nottingham led by astrophysicist Christopher Conselice compared older Hubble photos with new ones, and used mathematical models to infer how many galaxies there are that we are unable to see using our existing observational equipment.
While images captured with the space telescope 20 years ago determined that there must be at least 100 billion galaxies in the universe, and around 200 billion by some estimates, the research team has determined that there are approximately two billion galaxies out there, 90% of which are too faint or far away to be seen with modern-day telescopes.
“We now know that there are at least 10 times more galaxies in the universe than we had thought for the last 20 years, and before that we didn’t really have any idea,” Conselice, lead author of a new study accepted for publication in The Astrophysical Journal, explained to the Times. “So the more we learn about the universe… the more interesting it becomes.”
90% of all galaxies have yet to be studied, according to the authors
The researchers used Hubble’s Wide Field Camera 3, which was able to observe the universe in near-infrared wavelengths to create a 3D map of space dating back nearly 13 billion years. They found that the early universe was filled with a tremendous amount of smaller galaxies which had lower masses than the larger galaxies of today.
Over time, those galaxies merged into larger galaxies and their overall population density started to dwindle, the study authors explained. Their findings suggest that, while the overall mass of the universe remains unchanged, galaxies themselves have not been evenly distributed throughout the history of the cosmos.
“These results are powerful evidence that a significant galaxy evolution has taken place throughout the universe’s history, which dramatically reduced the number of galaxies through mergers between them – thus reducing their total number,” Conselice said in a statement. “This gives us a verification of the so-called top-down formation of structure in the universe.”
“It boggles the mind that over 90 percent of the galaxies in the universe have yet to be studied,” he added. “Who knows what interesting properties we will find when we discover these galaxies with future generations of telescopes? In the near future, the James Webb Space Telescope will be able to study these ultra-faint galaxies.” In fact, Conselice told the Times, the Webb telescope will “more than double the number of galaxies that we can see today.”
Furthermore, their research helps explain a phenomenon known as Olbers’ paradox, which asks why the sky is dark at night if the universe is home to an infinite amount of stars. The authors of the new study have determined that, while every part of the sky does contain part of a galaxy, the light from those galaxies is invisible to the human eye due to its absorption by intergalactic dust and gas, and other factors that make the sky appear dark.
Image credit: NASA