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Airdate: Sep 22, 2003
Scientist: Ben R. Oppenheimer

Missing Matter: Nature of Dark Objects

Missing Matter: Nature of Dark Objects
When you look at the seemingly endless darkness of space, you are actually observing gargantuan hidden bodies of matter.



Astronomers say there’s more to our universe than meets the eye. In order for our galaxy to be spinning at the rate it does, it has to have - according to the laws of physics - more mass than we can currently account for. And so, astronomers are searching for missing matter, which by their calculations, makes up nine-tenths of our galaxy. I’m Jim Metzner, and this is Pulse of the Planet. Ben Oppenheimer is an astronomer at the University of California in Berkeley.

"For most of their lives, stars maintain a state like the sun. It's called the Main Sequence, where they're simply burning their nuclear fuel -- fusing atoms into the products of nuclear fusion and thereby producing the light that we see. Once they burn up that fuel, they evolve into new stage of stellar evolution. They eventually become enormous stars - Red Giant stars, the size of the solar system, actually."

After that, Oppenheimer says, most stars will eventually collapse to become faintly glowing White Dwarf stars.

"99% of the stars will actually go through these various stages in stellar evolution and end up as white dwarfs. They shed off some percentage of the mass, and what's left in the center is basically the core of the star. That core slowly contracts into a white dwarf. Then it remains a white dwarf, we believe, for the rest of time. And they're approximately the size of the Earth, but on average, half the mass of the sun, so they're extremely dense."

These compact White Dwarf stars emit such low levels of light that they can’t be seen from the earth. So astronomers believe that they may account for much of the invisible mass in our galaxy.

Pulse of the Planet is presented by the National Science Foundation. I’m Jim Metzner.