‘Fossil’ galaxy from early universe discovered

Washington, May 2  In what could provide a new window into how the first galaxies were formed, astronomers have discovered a first-ever ‘fossil’ galaxy left over from the early universe.

The faintest known galaxy has been named Segue 1.

“Segue 1 is the least chemically evolved galaxy known. After the initial few supernova explosions, it appears that only a single generation of new stars were formed, and then, for the last 13 billion years, the galaxy has not been creating stars,” explained Josh Simon from Carnegie Mellon University.

Astronomers hoping to learn about the first stages of galaxy formation after the Big Bang use the chemical composition of stars to help them unravel the histories of the Milky Way and other nearby galaxies.

Using these chemical analysis techniques, the team, using Carnegie’s 6.5-metre Magellan telescopes in Chile, was able to categorise Segue 1’s uniquely ancient composition.

“Because it has stayed in the same state for so long, Segue 1 offers unique information about the conditions in the universe shortly after the Big Bang,” the study noted.

“Segue 1’s uniquely low iron abundance relative to other elements shows that its star formation must have stopped before any of the iron-forming supernovae occurred,” Simon informed.

In contrast to all other galaxies, the new analysis shows that Segue 1’s star formation ended at what would ordinarily be an early stage of a galaxy’s development.

Segue 1 possibly failed to progress further because of its unusually tiny size.

This truncated evolution means that the products of the first explosions in Segue 1 have been preserved. Intriguingly, very heavy elements like barium and strontium are nearly absent from Segue 1’s stars.

“The heaviest elements in this galaxy are at the lowest levels ever found,” said Anna Frebel from Massachusetts Institute of Technology. “This gives us clues about what those first supernovae looked like,” she added in a paper published in The Astrophysical Journal.