Carnegie Institution for Science | 2015 Mar 23
A Carnegie-based search of nearby galaxies for their oldest stars has uncovered two stars in the Sculptor dwarf galaxy that were born shortly after the galaxy formed, approximately 13 billion years ago. The unusual chemical content of the stars may have originated in a single supernova explosion from the first generation of Sculptor stars. The team, which includes Carnegie’s Josh Simon, Ian Thompson, and Stephen Shectman, will publish their work in The Astrophysical Journal on Thursday.
The Sculptor dwarf is a small galaxy that orbits around our own Milky Way, just as the Moon orbits around the Earth. Large galaxies like the Milky Way can contain several hundred billion stars, but Sculptor is home to just a few million. Because Sculptor’s stars are all located the same distance away from us, their ages can be determined by studying the pattern of their colors and brightnesses. This technique tells astronomers that Sculptor, like many dwarf galaxies, stopped evolving long ago. While the Milky Way has been forming stars throughout the universe’s 14 billion year existence, Sculptor’s youngest stars are 7 billion years old. Dwarf galaxies thus provide scientists an opportunity to see what galaxies looked like in the early epochs of the universe.
Stars in all galaxies are born out of collapsing clouds of dust and gas. Only a few million years after they begin burning, the most-massive of these stars explode in titanic blasts called supernovae. These explosions seed the surrounding gas with the elements that were manufactured by the stars during their lifetimes. Those elements are then incorporated into the formation of the next generation of stars. Generally this process is cyclical, with each generation of stars contributing more elements to the raw material from which the next set of stars will be formed. ...
Chemical Signatures of the First Supernovae in the Sculptor Dwarf Spheroidal Galaxy - Joshua D. Simon et al
- arXiv.org > astro-ph > arXiv:1412.5176 > 16 Dec 2014