'Wimpy' Dwarf Fossil Galaxy Sheds Light on the Early Universe

Astronomers may have learned a bit more about our early universe by examining a dwarf fossil galaxy. Known as Segue 1, the galaxy is the faintest ever detected and has only about 1,000 stars.

Segue 1 is located about 75,000 light years from Earth. It has a rare chemical composition, with a surprisingly small amounts of metallic elements. In order to learn a bit more about this galaxy, the researchers analyzed the chemical composition and shed light on the evolution of galaxies in the early stages of our universe.

Usually, stars form from gas clouds and then burn up as supernova explosions after about a billion years. These explosions spew elements that are the basis for a new generation of star formation. Yet it seems this isn't the case for Segue 1. Instead, the galaxy's process of star formation halted at an early stage of development.

"It's chemically quite primitive," said Anna Frebel, one of the researchers, in a news release. "This indicates the galaxy never made that many stars in the first place. It is really wimpy. The galaxy tried to become a big galaxy, but it failed."

Yet the fact that this galaxy didn't grow any further actually sheds some light on what galaxies were like in the early universe. Segue 1 has stars that are distinctively poor in metal content, and all of the elements in the galaxy that are heavier than helium appear to have derived either from just one or only a few supernova explosions.

That said, more work needs to be done before any conclusions are drawn about the state of early galaxies in the universe. In fact, Segue 1 indicates that there may be a greater diversity of evolutionary pathways among galaxies in the earlier universe than has been thought.

"We would really need to find more of these systems," said Frebel in a news release. "Or if we never find another one [like Segue 1], it would tell us how rare it is that galaxies fail in their evolution. We just don't know at this stage because this is the first of its kind."

The findings are published in The Astrophysical Journal.