How many galaxies are in the universe? Way, way more than anyone knew.
For decades, astronomers had put the number at 100 billion to 200 billion. But new research using data from the Hubble Space Telescope and other observatories shows that number is about 10 times too low.
That means there are at least 1 trillion galaxies out there ― and possibly as many as 2 trillion.
To arrive at the astonishing new number, researchers led by University of Nottingham astrophysicist Dr. Christopher Conselice used deep-space images taken by Hubble and other published data to make accurate measurements of the number of galaxies at different periods in the 13.8 billion-year history of the universe.
Then, with the help of mathematical models, the researchers were able to show that for the number of galaxies we now see to match up with their masses there had to be many more galaxies that are too faint and too far away to be seen with today’s telescopes.
“It boggles the mind that over 90 percent of the galaxies in the universe have yet to be studied,” Conselice said in a NASA news release. “Who knows what interesting properties we will find when we discover these galaxies with future generations of telescopes?”
Those future telescopes include the much-anticipated James Webb Space Telescope (see below), which should be able to show us these previously unknown and still-invisible galaxies following its launch in 2018.
The new research is a verification of the so-called “bottom-up” scenario for the formation and evolution of galaxies, Conselice told The Huffington Post. That scenario holds that there were many more galaxies in the young universe but that the number is lower now because many galaxies merged.
The new research may also help resolve Olbers’ paradox (see brief animation below), which has to do with why the night sky is dark even though the number of stars in the universe is so vast that there should be at least one for every point in the sky.
The research suggests that there are enough stars for one to exist at each point in the sky, according to the release. But the light from these stars is invisible to us ― in part because of the continuing expansion of the universe and because the light is absorbed by intergalactic dust and gas.
Now we know!