AAS News

Penn State, Rutgers astronomy teams discover ancestors of galaxies like Milky Way

Astronomers at Penn State and Rutgers universities have discovered galaxies in the distant universe that are ancestors of spiral galaxies like the Milky Way.
The newly discovered galaxies are quite small -- one-tenth the size and one-twentieth the mass of the Milky Way. They also have fewer stars -- only one-fortieth as many as are in the Milky Way. From ground-based telescopes, they look like individual stars in size. Recent images made by the Hubble Space Telescope, however, reveal them as regions of active star formation.

"Finding these objects and discovering that they are a step in the evolution of our galaxy is akin to finding a key fossil in the path of human evolution," Gawiser said. The team led by Gronwall and Gawiser determined that these galaxies were fertile breeding grounds for new stars, which burned hot and bright.These stars ionized the hydrogen atoms around them, stripping them of their electrons and causing them to emit a tell-tale sharp band of ultraviolet light known as Lyman alpha. The researchers also noted that several of these galaxies, sometimes 10 or more, pulled together over the ensuing few billion years to form a single spiral galaxy.