October 27, 2012
Milky Way Caught In The Act Of Consuming A Light Snack
redOrbit Staff & Wire Reports - Your Universe Online
The Milky Way apparently has one voracious appetite, as researchers from a prominent American university have discovered our home galaxy slowly consuming the remnants of an ancient star cluster.
While researchers have previously discovered evidence that the Milky Way has gobbled up dwarf galaxies, lead author Ana Bonaca said that they believe that the narrowness of the newly discovered stream means that it originated from a star cluster, not part of a larger galaxy.
"The Milky Way is constantly gobbling up small galaxies and star clusters," said Bonaca, a graduate student at the Connecticut-based Ivy League school. "The more powerful gravity of our Milky Way pulls these objects apart and their stars then become part of the Milky Way itself."
"Our discovery is more of a light snack than a big meal for the Milky Way," added Marla Geha, co-author of the study and an associate professor of astronomy at Yale. "Studying this digestion process in detail is important because it gives us new insight into how all galaxies form and evolve.”
The newly discovered stellar stream has been dubbed the Triangulum stream, and according to Yale officials it is the first of its kind to have been discovered in the southern Galactic sky region.
That area has been difficult to examine due to the comparative lack of deep-sky imaging in that area, which enables researchers to locate fainter stars. The astronomers believe that the band of stars could help scientists "reconstruct how the Milky Way´s mass is distributed, further revealing its dynamic structure."
"Galaxies are believed to form hierarchically through the merger of smaller galaxies and still smaller star clusters. Stellar streams form as they are ripped apart by the gravitational force of galaxies," university officials concluded in a statement, adding that the researchers believe that this process "may be the primary way galaxies such as the Milky Way grow in mass."
Their research, which was sponsored by the National Science Foundation (NSF) and the Alfred P. Sloan Foundation, is currently available online at the arXiv preprint server. It will also be published in a future edition of the Astrophysical Journal Letters.
Image 2 (below): A map of stars in the outer region of the Milky Way as traced by the Sloan Digital Sky Survey. Streams of stars are seen throughout both the Northern (top) and Southern Galactic hemispheres, corresponding to small galaxies and star clusters which are in the process of being ingested by the Milky Way. The newest discovery is designated as the Triangulum Stream.