Astronomers discover there are 10 times more galaxies than previously thought
The universe has 2 trillion — 12 zeros! — galaxies, a new report concludes.
We know so very, very little about the universe, as a paper published today in the Astrophysical Journal reminds us. We thought the observable universe contained billions of galaxies. But it seems there are at least 2 trillion galaxies out there — 10 times greater than astronomers’ previous estimates.
Examining decades of data from the Hubble Space Telescopes and other observatories around the world, an international team of scientists now believe that 90 percent of the galaxies in the universe are “too faint and too far away to be seen.”
But they are out there.
Let’s pause for a moment to let this all sink in.
A galaxy can house hundreds of billions of stars, and each star system can contain dozens of planets. Astronomers have estimated there may be a billion Earth-like planets rocky planets orbiting in a star’s “habitable zone” in our galaxy alone. And now, we learn, there are around 2 trillion (12 zeros!) galaxies. Whoa. (As Forbes points out, that’s 200 galaxies for each human on Earth.)
"It boggles the mind that over 90 percent of the galaxies in the universe have yet to be studied,” Christopher Conselice, who led the study at the University of Nottingham, says in a press release. “Who knows what interesting properties we will find when we discover these galaxies with future generations of telescopes?”
How do astronomers count the number of galaxies?
Previous estimates of the number of galaxies in the universe come from a series of Hubble photos. The first one was “Hubble Deep Field,” which was captured in 1995.
Vox’s Joss Fong and Dion Lee tell the story of Deep Field in the following video, which you should watch. But in summary: Hubble scientists pointed the space telescope at a tiny, unassuming spot in the night sky where there were no known celestial objects. They saw thousands of previously unknown galaxies.
That so many galaxies could be found in such a tiny stretch of the sky allowed astronomers to begin to estimate the population of galaxies in the universe. The Deep Field observation (and its follow-up, the Ultra Deep Field, in 2004) led them to put the number of galaxies at around 100 billion.
