For the last 25 years, the Hubble Space Telescope has allowed us to look deep into the universe, helping us resolve some long-standing mysteries – such as the prevalence of black holes – whilst raising more questions about others. It also simply allowed us to see more of what’s out there, fanning theories of thousands of far away galaxies too dim to properly make out. But new research indicates that we might have been overestimating this.
“Our work suggests that there are far fewer faint galaxies than we once previously thought,” explained Brian O'Shea, who co-authored the study published in Astrophysical Journal Letters. “Earlier estimates placed the number of faint galaxies in the early universe to be hundreds or thousands of times larger than the few bright galaxies that we can actually see with the Hubble Space Telescope. We now think that number could be closer to ten times larger.”
How bright a galaxy appears depends on a number of factors, including its distance from us and the number of stars present in the cluster. We have a pretty good idea of how many bright, easily observed galaxies there are, but it’s far harder to calculate the number of dimmer ones that are, by their very nature, trickier to observe.
The team of researchers from Michigan State University ran a computer simulation of galaxies forming during the beginning of the universe, factoring in thousands of clusters and how their individual gravities and radiation interact. They found that the simulation pretty accurately predicted the number of bright galaxies, the ones we have managed to observe, but what they didn’t find was an exponentially increasing number of faint ones.
This suggests that it's likely incorrect that there are a thousand times more faint galaxies compared to bright ones, and that the number is perhaps a more modest 10 to 100 times greater. The researchers hope that when the James Webb Space Telescope comes online, it will allow astronomers the chance to have a far more detailed look into space, and that the data it collects will add more to the debate.