White Dwarfs Yield Key to Age of Ancient Stars
Astronomer used white dwarfs to calculate age of Milky Way's inner halo
By Mark Russell,  Newser Staff
Posted May 31, 2012 11:25 AM CDT
Messier 4 is a globular star cluster that an astronomer used, along with white dwarfs, to determine the age of stars in the Milky Way's inner halo.   (DeepSkyVideos)
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(Newser) – Accurately measuring the age of low-mass, hydrogen burning stars is notoriously difficult, but now astronomers say they have come up with a technique for measuring those difficult stars using white dwarfs, reports the LA Times. A white dwarf is a star that has burned through all of its hydrogen, shed its outer layers, and become a dense lump of carbon and oxygen, and astronomers consider them relatively simple objects to measure. Jason Kalirai from Baltimore's Space Telescope Science Institute compared newly formed white dwarfs from the inner halo of the Milky Way with a well-studied cluster of stars called Messier 4.

Because more massive stars burn faster, Kalirai was able to calculate how old the stars were that became the white dwarfs. From there, he was able to figure out how old the stars in the inner halo were: 11.4 billion years (plus or minus 700 million years). "If we want to assess when components of the Milky Way formed, we need the ages of the stars," said Kalirai. You can check out an abstract of Kalirai's original article in Nature.