WASHINGTON — The universe may glitter with far more stars than even Carl Sagan imagined when he rhapsodized about billions upon billions.

A new study suggests there are a mind-blowing 300 sextillion of them, or three times as many as scientists previously calculated. That is a 3 followed by 23 zeros. Or 3 trillion times 100 billion.

The estimate, contained in a study published online Wednesday in the journal Nature, is based on findings that there are many more red dwarf stars — the most common star in the universe — than once thought.

But the research goes deeper than that. The study by Yale University astronomer Pieter van Dokkum and Harvard astrophysicist Charlie Conroy questions a key assumption that astronomers often use: that most galaxies have the same properties as our Milky Way. And that conclusion is deeply unsettling to astronomers who want a more orderly cosmos.

When scientists previously estimated the total number of stars, they assumed that all galaxies had the same ratio of dwarf stars as the Milky Way, which is spiral-shaped. Much of our understanding of the universe is based on observations made inside our own galaxy and then extrapolated to other galaxies.

But about one-third of the galaxies in the universe are elliptical, not spiral, and van Dokkum found they aren’t really made up the same way as ours.

Using the Keck telescope in Hawaii, van Dokkum and a colleague gazed into eight distant, elliptical galaxies and looked at their hard-to-differentiate light signatures. The scientists calculated that elliptical galaxies have a lot more red dwarf stars than predicted.

“We’re seeing 10 or 20 times more stars than we expected,” van Dokkum said.

Generally scientists believe there are 100 billion to a trillion galaxies in the universe. And each galaxy was thought to have 100 billion to a trillion stars. Sagan usually said there were 100 billion galaxies, each with 100 billion stars.