Hubblecast 96: How many galaxies are there?

A new analysis of Hubble’s deep-field images revises the total number of galaxies in the observable universe from 200 billion to at least 2 trillion — ten times more than previously thought. The episode explains how most of these galaxies are too faint and distant to be seen even with Hubble, and what this revised census implies about the history of galaxy formation in the early universe.