White dwarf stars said oldest and closest

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NORMAN, Okla., April 11 (UPI) -- University of Oklahoma astronomers say they have identified two white dwarf stars considered the oldest and closest known to man.

These 11- to 12-billion-year-old stars, just 100 light years from Earth, are the closest known examples of the oldest stars in the universe forming soon after the Big Bang, a university release said.

White dwarf stars are the burned-out cores of stars similar to the sun.

"A white dwarf is like a hot stove; once the stove is off, it cools slowly over time," OU physics and astronomy Professor Mikremin Kilic said.

"By measuring how cool the stove is, we can tell how long it has been off. The two stars we identified have been cooling for billions of years."

The two white dwarfs are located in the constellations Taurus and Ursa Major and Kilic and his colleagues obtained infrared images using NASA's Spitzer Space Telescope to measure the temperature of the stars.

"It is like a crime scene investigation," Kilic said. "We measure the temperature of the dead body -- in our case a dead star, then determine the time of the crime. These two white dwarf stars have been dead and cooling off almost for the entire history of the universe."