How Many Galaxies Actually Exist in the Universe?

For decades, scientists told us the universe contained about one hundred billion galaxies. Then the Hubble Space Telescope stared at a blank patch of sky for ten days and everything changed. The Hubble Deep Field revealed thousands of galaxies hiding in apparent emptiness, and the count began climbing, from one hundred billion to two trillion, and possibly far beyond. But here's the unsettling truth: over ninety percent of galaxies in the observable universe may have never been seen by any human instrument. They are too faint, too small, too diffuse, and too distant. Ultra-faint dwarf galaxies containing only a few hundred stars hide in our own cosmic backyard. Giant galaxies the size of the Milky Way vanish because their light is spread too thin. Billions of early galaxies merged into larger structures and no longer exist. And beyond the cosmic horizon, the universe almost certainly continues, possibly containing quintillions more galaxies whose light will never reach us. In this documentary, we trace the full history of the galaxy count, from Edwin Hubble's discovery that the Milky Way was not alone, through the revolutionary Deep Field observations, to the James Webb Space Telescope's shocking discovery of unexpectedly bright galaxies at cosmic dawn. We explore why every deeper image has found more galaxies, why the faintest dwarfs may outnumber visible galaxies a hundred to one, why the number depends on how you define "galaxy," and why the real answer may be permanently unknowable. The question is not how many galaxies we can count. The question is how much of the universe remains hidden. Sources: Conselice, C.J. et al. (2016). "The Evolution of Galaxy Number Density at z less than 8 and Its Implications." The Astrophysical Journal, 830(2), 83. University of Nottingham / arXiv:1607.03909 Postman, M., Lauer, T. et al. (2021). "New Horizons Observations of the Cosmic Optical Background." The Astrophysical Journal, 906(2), 77. Space Telescope Science Institute NASA/ESA Hubble Space Telescope — Hubble Deep Field, Ultra Deep Field, and eXtreme Deep Field official documentation: The Hubble Deep Fields Naidu, R.P. et al. (2025). "MoM-z14: The Most Distant Galaxy Known." arXiv:2505.11263 — James Webb Space Telescope JADES survey confirmation Siegel, E. (2024). "Our Universe Has More Galaxies Than Carl Sagan Ever Imagined." Big Think / Starts With A Bang — analysis of 6–20 trillion galaxy estimates incorporating JWST data #Galaxies #Universe #HubbleDeepField #JamesWebbSpaceTelescope #JWST #SpaceDocumentary #Cosmology