Q How many galaxies are in the universe?
โ Gus Powvens, Madison, Wis.
Aย Jim Lattis, director of the UW Space Place at the University of Wisconsin-Madison:
Galaxies are clouds of stars that range in both size and composition. Some contain hundreds of millions of stars while the largest galaxies can contain trillions of stars. And while itโs not entirely clear, most galaxies seem to be associated with a massive black hole, so itโs possible thatโs one of their distinguishing features.
Counting the number of galaxies in the universe is tough because we canโt see all of them. At a certain point, distant galaxies disappear from our field of view. They sort of cross over the horizon, and we canโt see anything beyond.
But in the visible universe, how many galaxies are there? Researchers explore that question by looking at a small patch of sky, counting the galaxies present, and then suppose that circumstances are the same around the whole sky. You count up all the galaxies you can see in the small patch of sky and then multiply by how much bigger the entire sky is.
This was done with an image taken with the Hubble Space Telescope. This image, called the Hubble Deep Field, revealed very distant galaxies, and the math estimated that there were around 120 billion galaxies.
Recently thereโs been a study using new data from the Hubble telescope, but this time trying to figure out how many galaxies are being missed when those calculations and estimations are made. When galaxies are nearby we can see more, including smaller, dimmer ones. But as they get farther away, those smaller, dimmer galaxies are harder to see and disappear from the count.
With this new research the number is now closer to 2 trillion galaxies in the visible universe, a factor of 10 more than we would have counted before.
