Washington — Ghostly remnants of ancient, burned-out stars litter the edge of the Milky Way and researchers say such objects may account for more than a third of the universe's "missing matter."
Astronomers surveying images taken of the southern sky discovered 38 dead stars, called white dwarfs, about 450 light years from Earth and within the halo surrounding the Milky Way, the home galaxy of the sun.
If this concentration of the faint objects is typical for galaxies, then white dwarfs could represent from 3 percent to 35 percent of the missing matter sought by astronomers for 70 years, said Ben Oppenheimer of the University of California, Berkeley.
White dwarfs are the chilling cinders of a dying star. When stars up to eight times the size of the sun burn up all their nuclear fuel, they first erupt into red giants and then collapse into cool white dwarfs.
Temperatures on the surface of some stars burning hydrogen can soar to more almost 60,000 degrees. After some 10 billion years, when the fuel is gone, the stars collapse to the size of the Earth and cool to about 8,000 degrees.
At that temperature, these objects do not emit enough light or other radiation to be easily detected by telescopes. That is why the objects found by Oppenheimer and his co-authors have not been seen before. Oppenheimer's study appears today in the journal Science.
Astronomers have been searching for the "cold, dark matter" of the universe since 1933, when astronomers found that there was not enough visible, shining matter in galaxies to explain the gravitational movement of objects in the universe.
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