The earliest estimates of the number of galaxies in the Universe were very small. For centuries, astronomers thought there might be just one—our own. Most recent estimates built off observations from 1995, when NASA’s Hubble Space Telescope stared at a dark patch of sky for hours and returned a picture of thousands of glittering galaxies no one had ever seen before. Further measurements led astronomers to believe there are between 100 billion and 200 billion galaxies in the observable Universe that human-made technology can detect.

And that was the working estimate for the next two decades, until this week. Astronomers at the University of Nottingham now say the number of galaxies in the observable Universe is 2 trillion, more than 10 times as many as previously thought.

To reach this figure, researchers studied decades of images of galaxies—clusters of millions or billions stars, gas, and dust—taken by Hubble and other powerful telescopes. Their research, announced Thursday, will be published in the Astrophysical Journal.

There’s only one way to count galaxies with existing technology: Point a telescope at a small chunk of sky, tally up the number you see, and then extrapolate that across the whole sky. But when the Nottingham researchers examined the masses of the galaxies in those patches of sky, they realized there must be missing galaxies that are “too faint and too far away” to be imaged by modern technology, even the most powerful telescopes in the world.