SEXTILLION STARS

WASHINGTON –  A new study reveals that there are 300 sextillion stars in the universe.  Three times more than previously calculated.

Sextillion.  That’s a 23 zeros.   A 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.

Astronomers have been counting and re-counting the stars for the last five years – much like the Bush-Gore election results.

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 more red dwarf stars than predicted. A lot more.

“We’re seeing 10 or 20 times more stars than we expected,” van Dokkum said.  He then had his associates literally count the stars – one by one.

Generally scientists believe there are 100 billion to a trillion galaxies in the universe. And each galaxy — the Milky Way included — was thought to have 100 billion to a trillion stars. Sagan, the Cornell University scientist and best-selling author who was often impersonated by comedians as saying “billions and billions,” usually said there were 100 billion galaxies, each with 100 billion stars.

Van Dokkum’s work takes these numbers and adjusts them. That’s because some of those galaxies the elliptical ones, which account for about a third of all galaxies — have as many as 1 trillion to 10 trillion stars, not a measly 100 billion. When van Dokkum and Conroy crunched the incredibly big numbers, they found that it tripled the estimate of stars in the universe from 100 sextillion to 300 sextillion.

That’s a huge number to grasp, even for astronomers who are used to dealing in light years and trillions, Conroy said.

“It’s fun because it gets you thinking about these large numbers,” Conroy said. Conroy looked up how many cells are in the average human body — 50 trillion or so — and multiplied that by the 6 billion people on Earth. And he came up with about 300 sextillion.

So the number of stars in the universe “is equal to all the cells in the humans on Earth” a kind of funny coincidence, Conroy said.

For the past month, astronomers have been buzzing about van Dokkum’s findings, and many aren’t too happy about them, said astronomer Richard Ellis of the California Institute of Technology.

Van Dokkum’s paper challenges the assumption of “a more orderly universe” and gives credence to “the idea that the universe is more complicated than we think,” Ellis said. “It’s a little alarmist.”

Ellis said it is too early to tell if van Dokkum is right or wrong, but his work is shaking up the field “like a cat among pigeons.”

Astronomers on both sides of the “sextillion” issue are back to counting stars.  They are all eager to come up with the EXACT number of stars in the universe.

Van Dokkum agreed, saying, “Frankly, it’s a big pain.”

Ellis said the new study does make sense. Its biggest weakness might be the assumption that the chemical composition of dwarf stars is the same in elliptical galaxies as in the Milky Way. That might be wrong, Ellis said. If it is, it would mean there are only five times more red dwarf stars in elliptical galaxies than previously thought, instead of 10 or 20, van Dokkum said.