How to Make a Milky Way -- Schilling 2008 (108): 1 -- ScienceNOW

AUSTIN, TEXAS--Looking 12 billion years back in time, astronomers have found the ancestors of spiral galaxies like our own Milky Way. They liken the discovery, presented here at the 211th meeting of the American Astronomical Society, to finding key fossils in the evolutionary history of Homo sapiens.
The very first galaxies--formed shortly after the big bang--were small and dim. Through mergers, they grew into the large galaxies we see today. Astronomers using the biggest telescopes can see these original building blocks at very large distances, where the universe appears as it did billions of years ago (ScienceNOW, 28 November 2007). But there's a snag: Astronomers have found such a stunning variety of early galaxies that they are unclear about which of these faint objects are the precursors of spiral galaxies like our Milky Way and which are the ancestors of other types of galaxies, such as giant ellipticals like M87 (ScienceNOW, 5 November 2001).
Now, astrophysicists Eric Gawiser of Rutgers University in New Brunswick, New Jersey, and Caryl Gronwall of Pennsylvania State University in State College say they've solved the puzzle. The researchers used the Hubble Space Telescope, along with other ground- and space-based scopes, to analyze lightweight collections of stars known as Lyman alpha emitters. These clusters are 10 times smaller and 20 to 40 times less massive than the Milky Way. Gawiser, Gronwall, and their colleagues showed that the starlight emitted from these star collections, and the way they are clustered in space, indicates that they must have been the building blocks for larger galaxies such as the Milky Way.
The new results will help astronomers better understand the origin and evolution of galaxies--one of the outstanding problems in cosmology, says astronomer Sandra Faber of the University of California, Santa Cruz. "It's like discovering embryonic cells: It starts to become interesting when you know what they will evolve into."