If you could see through the lens of a very powerful telescope, to an area of sky the size of a grain of sand held at arm’s length, a new universe would be revealed to you. For in that tiny patch of seemingly empty sky, there are thousands of galaxies visible, albeit with many hours of light collection. Observing the most distant of these galaxies, at the edge of the universe, allows us to estimate the number of Galaxies present in the distant past, when the universe was very young. As our observations improve, and our ability to simulate the conditions of the early universe grows, we refine our estimates and close in on the true nature of space and time.
A recent study performed by Michigan State University is now claiming that our estimates of early galaxies in the universe is 10 to 100 times too large, meaning the universe may be a lot emptier than we thought.
The team used the National Science Foundation’s Blue Waters computer to run simulations of how galaxies formed in the early universe. Thousands of galaxies were simulated at a time, and their interactions through gravity and radiation were calculated. The simulations were consistent with the observations of bright early galaxies seen by Hubble and other deep sky surveys.
However, to their surprise, even though they matched the observations, there were far fewer faint galaxies in the simulations, reducing the total number of galaxies by at least a factor of ten. In the theory, the number of faint galaxies should increase exponentially as the brightness decreases. This is basic statistics; if we see ten of the biggest galaxies, there must be a hundred or more smaller ones we can’t see. This is also consistent with models of galaxy formation.
But with the new results, it seems that there are very few dim galaxies, suggesting they aren’t forming as quickly or they are quickly merging into larger and brighter galaxies. Future studies with Hubble and the James Webb Space Telescope (JWST) will probe deeper into the early universe, tightening our constraints on the initial conditions of galaxy formation and in turn our simulation parameters.
As far as we’ve come in the scientific world, there is still a lot to learn, and we always move forward with reverence for the cosmos, and the understanding that the universe is full of surprises.