If you believe in wishing upon a star, Pieter van Dokkum of Yale University has some good news: There’s suddenly about three times as many of them as you may have thought.
Using newly upgraded photographic capabilities at the W.M. Keck Observatory in Hawaii, Mr. van Dokkum led a survey that found a relatively small but plentiful type of star, known as a red dwarf, is far more common in some galaxies than had been assumed by their proportion in our own Milky Way.
The discovery, reported in Wednesday’s issue of Nature magazine, has implications well beyond Jiminy Cricket and others known to correlate wishes with stars. The billions of additional stars drastically raise the number of possible planets where life may have formed. The newfound stars also might account for some of the “dark matter” in the universe that has driven physicists to build hugely expensive machines designed to seek it out—though those who work on the problem of this unseen matter note that the new stars don’t completely solve it.
The discovery at Keck is the result of “getting a better camera” to view the universe, said Mr. van Dokkum, who trained the camera on eight elliptical-shaped galaxies and then multiplied the number of newly discovered stars by the number of other such galaxies across the universe. Mr. van Dokkum, a professor of astronomy and physics at Yale, is particularly intrigued by the possibilities of life-bearing planets that may be associated with some new stars, as the earth is associated with the sun.
Red dwarfs may be small, he said, but one called Gliese 581, only about one-third the size of the sun, recently made headlines when it was found to have several orbiting planets, including one that appears to have the range of temperature conditions necessary to support life.
Not everyone is so enthusiastic about the implications. One discoverer of Gliese 581, R. Paul Butler of the Carnegie Institution of Washington, said the stars found by Mr. van Dokkum are so far away, and the overall numbers so large, that the additional finding is meaningless in the search for extraterrestrial life.
“Let’s be real,” said Mr. Butler, a staff scientist at Carnegie’s department of terrestrial magnetism. “There’s so many stars in the universe that if the question of whether life exists or not hinged on whether there were triple the number we previously thought, or not, then life is incredibly rare.”
Does Dark Matter Exist?
Then there is the matter of dark matter. The concept stems from telescope observations that appear to show light beams being bent and stars pulled by gravity in ways that can’t be accounted for by visible objects such as stars and planets. Astrophysicists theorize that there is matter out there that they cannot see—"dark matter"—and that is exerting the mysterious gravitational tugs. Explaining what dark matter actually consists of is one of the fundamental questions of physics that scientists hope to solve by smashing together pieces of atoms with the $5-billion Large Hadron Collider, the new 17-mile-long particle accelerator built beneath the French-Swiss border near Geneva.
Those involved with such work, however, see little reason to believe their studies will be quickly rendered moot. That’s because the universe’s dark matter appears to be about four times the mass of visible matter. So even tripling the number of stars, especially with low-mass stars such as red dwarfs, does very little to explain all that dark matter, said Craig J. Hogan, a professor of astronomy and astrophysics at the University of Chicago.
“This increase really doesn’t amount to a hill of beans in this crazy world,” said Mr. Hogan, who is leading a search for dark matter in his role as a particle astrophysicist at the Fermi National Accelerator Laboratory, near Chicago.
Mr. van Dokkum doesn’t challenge the bottom line of such assessments, acknowledging there’s still a lot of dark matter that requires accounting for. But since red-dwarf stars tend to be concentrated toward the middle of galaxies, the finding might explain why many of the gravitational effects attributed to dark matter are seen toward galactic centers, said Charles F. Conroy, a researcher at the Harvard-Smithsonian Center for Astrophysics.
Mr. Conroy, who worked on the Keck project, said that “knowledge of the precise amount of dark matter within galaxies is important for understanding galaxy formation and assembly.”
Mr. van Dokkum also concedes that his tripling of stars pales in comparison to the much larger uncertainty over how many stars that actually means. Scientists estimate the number of stars in the Milky Way as totaling 100 billion to 1 trillion, with a similar number of galaxies in the universe.
That suggests a universe of roughly 100 sextillion stars, with an approximate margin of error of about 10 times fewer or 10 times more, Mr. van Dokkum said. He said his proposed tripling of that estimated number is based on his finding at Keck that elliptical galaxies have about 10 times as many red stars as the Milky Way, while accounting for about a third of all the galaxies in the universe.
Either way, Mr. van Dokkum agreed, it’s good news for those who like to wish upon a star. “They already had 100 sextillion to choose from,” he said. “But for those who want even more, yes, it’s an improvement.”
