Renewable Revolution

A galaxy contains billions of stars, held together by gravity. Within each galaxy, there are planetary systems, like the Earth and its neighbor planets within the Milky Way. But ours is just one galaxy in an astronomical sea of stars reaching farther than the most powerful telescopes can see. We will probably never know just how many galaxies exist, but 3-D modeling by the Hubble Space Telescope over 20 years has come up with a new estimate, published in The Astronomical Journal. In 2016, astronomers studied computer-enhanced deep space images and determined that there are probably around two trillion galaxies in the universe , far more than the previous estimate of between 100 and 200 billion galaxies.

Galaxies far, far away:

֍ The landmark Hubble Deep Field imaging of the mid-1990s gave scientists their first analysis of galaxies, and Hubble's Ultra Deep Field in 2004 added a plethora of faint galaxies, leading to an estimate of 200 billion galaxies.

֍ The newest analysis of deep-space images from Hubble converted the images into 3-D. Using mathematical models, scientists were able to infer the existence of galaxies that current telescopes cannot see.

֍ “It boggles the mind that over 90 percent of the galaxies in the universe have yet to be studied,” the University of Nottingham astronomers wrote. “Who knows what interesting properties we will find ... with the next generation of telescopes?”

https://www.wisegeek.com/how-many-galaxies-are-in-the-universe.htm