NEW HAVEN, Conn., Dec. 1 (UPI) -- The observable universe may hold as many as three times the number of stars previously estimated by astronomers just a year ago, U.S. researchers say.
Astronomers at Yale University said a particular kind of galaxy may contain 10 times more red dwarf stars than thought, which would triple the number of stars in the universe as a whole, the Christian Science Monitor reported Wednesday.
The Yale researchers surveyed eight huge elliptical galaxies selected from two vast galaxy clusters 53 million to 321 million light-years from Earth.
Surveys of our own galaxy, the Milky Way, have found red dwarfs outnumber sun-like stars by about 100 to 1, Yale astronomer Pieter van Dokkum said.
But the dwarfs are so dim and other galaxies so distant that red dwarfs fail to appear when astronomers try to account for the stars other galaxies contain, he said.
Astronomers had to assume the abundance of red-dwarf stars in the Milky Way held true throughout the universe for every galaxy type, van Dokkum said.
"We always knew that was sort of a stretch, but it was the only thing we had. Until you see evidence to the contrary you kind of go with that assumption," he said.
He and colleague Charlie Conroy with the Harvard-Smithsonian Center for Astrophysics used an improved spectrometer at the Keck Observatory in Hawaii to to hunt for evidence of red dwarfs in the eight distant galaxies to come up with their new estimate.
Still, the results need to be taken with caution, van Dokkum acknowledges.
When it comes to red dwarfs, astronomers "have made the mistake of assuming that the Milky Way was typical of all galaxies in the universe," he said. "We shouldn't make the mistake of assuming that these eight elliptical galaxies are representatives for all elliptical galaxies in the universe."