Fingerprints of Ancient Stars Reveal the History of the Sculptor Galaxy

Astronomers have uncovered the leftover fingerprints of ancient stars that probably formed shortly after the Sculptor dwarf galaxy formed, about 13 billion years ago. The unusual content of the stars may actually have been created in a single supernova explosion from the first generation of Sculptor stars.

The Sculptor dwarf galaxy is a small galaxy that orbits our own Milky Way. In fact, it's so small that it just has a few million stars contained within it. Because the galaxy's stars are all located the same distance away from us, their ages can be determined by studying the pattern of their colors and their brightness. This technique tells researchers that Sculptor stopped evolving long ago.

Stars in all galaxies are born out of collapsing clouds of dust and gas. Only a few million years after they began burning, the most massive of these stars explode in massive blasts called supernovae. These explosions seed the surrounding gas with elements that are then incorporated into the next generation of stars.

In this latest study, the researchers examined five stars in the Sculptor galaxy, measuring the abundance of 15 elements in each one. They found that the two most primitive stars have less than half as much magnesium and calcium as would have been expected based on their iron content, and just 10 percent as much silicon as similar stars in other galaxies.

"The only way to explain the shortage of magnesium, calcium and silicon in these stars is if their heavy elements were made by fewer than four supernovae, and thos supernovae need to have been a rare kind of explosion," said Josh Simon, one of the researchers, in a news release. "Most likely, we are seeing the leftover traces of just a single supernova."

In fact, it's likely that the two primitive stars were probably formed from a gas cloud that had been seeded by heavy elements made by just one previously exploded star. The parent star is thought to be one of the very first stars in the galaxy.

The findings reveal a bit more about this galaxy and tell astronomers a bit more about supernovae and the early history of galaxies in general.

The findings are published in the Astrophysical Journal.

For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).