Astronomers wish they could watch galaxies in the process of being born, but since this happened so slowly and so long ago, they must extrapolate from galaxies in their current states to try to piece together their histories. This quest recently benefited from a new piece of the puzzle: a November, 2007 observation of faint protogalaxies from back when the universe was only 15 percent of its current age.
The images are the most sensitive example of a type of imaging called spectroscopy, where light is dispersed into its component colors and the relative amounts of each color are measured. In these spectra, the scientists found the distinct signature of protogalaxies, which they believe are the building blocks of full-grown galaxies.
This discovery backs up the theory that gas coalesces into blobs (protogalaxies) that then stick together and eventually become galaxies.