Airdate: Sep 23, 2003
Scientist: Ben R. Oppenheimer
Missing Matter: White Dwarfs
Faint light wafts through the universe as ancient stars burn eternally.
When astronomers peer into deep space with their telescopes, they’re only seeing a partial picture of what’s out there. I’m Jim Metzner and this is Pulse of the Planet. Astronomers refer to the brightness of celestial objects in degrees of their luminosity, using our sun as a benchmark. But much of what’s out there may be too dim to be seen from earth. Scientists call this material "dark matter."
"Once things are about a millionth the luminosity of the sun, then they're good candidates for dark matter. So things like the earth, which glow very, very faintly - basically because they have some heat which is radiating into interstellar space - they do have some luminosity, but it's so small compared to the standard unit of luminosity, which is the solar luminosity."
Astronomer Ben Oppenheimer of the University of California in Berkeley is working to identify this so-called "dark matter".
"Basically things like rocks, black holes, brown dwarfs, which are failed stars that cool off for eternity, and white dwarfs are very good dark matter candidates."
Oppenheimer’s research indicates that faintly glowing white dwarf stars may make up as much as thirty-five percent of dark matter. A white dwarf is what remains after a star has burned up most of its fuel in the process we call nuclear fusion.
"These white dwarfs, they're basically made of the remnants of the nuclear fusion reactions - mainly carbon and oxygen - and they're approximately the size of the Earth, but on average, half the mass of the sun."
And although white dwarfs are much smaller and dimmer than visible stars, astronomers believe that their faint glow continues throughout eternity.
Pulse of the Planet is presented by the National Science Foundation.