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Stellar Graveyard Reveals Clues About Milky Way's Ancient Birth



Stellar Graveyard Reveals Clues About Milky Way's Ancient Birth

by Nola Taylor Redd, Space.com Contributor | November 18, 2015 07:00am ET
Hubble View of Milky Way Core

Pin It By studying the motion of stars over nearly a decade in the Hubble SWEEPS Field, shown here, scientists have been able to better understand the early years of the Milky Way.

Credit: NASA, ESA, A. Calamida and K. Sahu (STScI), and the SWEEPS Science Team

View full size image

NASA's Hubble Space Telescope has peered far back in time, detecting clues about how the Milky Way galaxy came together, shortly after the universe's birth.

Astronomers trained Hubble on the Milky Way's dense central bulge and spotted a population of superdense stellar corpses called white dwarfs that are remnants of stars that formed about 12 billion years ago. These stars are archeological evidence of the first few billion years of the galaxy's history, researchers said.

"It is important to observe the Milky Way's bulge, because it is the only bulge we can study in detail," study lead author Annalisa Calamida, of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, said in a statement. "You can see bulges in distant galaxies, but you cannot resolve the very faint stars, such as the white dwarfs." [Stunning Photos of Our Milky Way Galaxy (Gallery)]

Like other spiral galaxies, the Milky Way harbors a dense central bulge surrounded by wispy spiral arms. Scientists think that such bulges formed first, while the outer arms came later.

"The Milky Way's bulge includes almost a quarter of the galaxy's stellar mass," Calamida said. "Characterizing the properties of the bulge stars can then provide important ways to understand the formation of the entire Milky Way galaxy and that of similar, more-distant galaxies."

But studying the Milky Way's core is a challenge; Earth's sun orbits on one of the outlying arms, with stars lying between Earth and the galaxy's star-packed heart.

White Dwarfs in Milky Way's Central BulgePin It An image of the heart of the Milky Way shows the location of ancient white dwarfs. At left is a ground-based image of the galaxy's central bulge; the upper right shows a small section of Hubble's view of this region, while the lower-right image depicts four white dwarfs spied by Hubble.

Credit: NASA, ESA, A. Calamida and K. Sahu (STScI), and the SWEEPS Science Team; A. FujiiView full size image

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