Stars Reveal Early History of Milky Way
A new way to find a star’s age can give clues to how our Milky Way galaxy built itself up over billions of years from smaller galaxies, a U.S. astronomer says. Using a new technique, Jason Kalirai of the Space Telescope Science Institute in Baltimore has examined the burned-out relics of sun-like stars, called white dwarfs, in the inner region of our Milky Way galaxy’s halo, a spherical cloud of stars surrounding the galaxy’s disk.
Kalirai targeted white dwarfs in the galaxy’s halo because those stars are believed to be among the galaxy’s oldest, some almost as old as the universe itself. These ancient stars provide a fossil record of our Milky Way’s infancy, he said. Kalirai said his study reveals the white dwarfs in the halo are 11.5 billion years old, having formed 2 billion years after the birth of the universe 13.7 billion years ago.