Some of the oldest stars were found in our galaxy

Credit: Serge Brunier (NASA)

Credit: Serge Brunier (NASA)

MIT researchers, including several undergraduates, have discovered three of the oldest stars in the Universe, those living in our own galactic neighborhood. This research was conducted using data obtained with the Clay telescope, one of the Magellan twins at the Carnegie Institution for Science's Las Campanas Observatory.

The team discovered the stars in the Milky Way's halo, the cloud of stars that envelops the entire main galactic disk. According to the team's analysis, the three stars formed between 12 and 13 billion years ago, when the first galaxies were taking shape.

The researchers have named the stars SASS (Small Accreted Stellar System stars), as they believe that each once belonged to its own small, primitive galaxy, which was later absorbed by the larger but still growing Milky Way. Today, the three stars are all that remain of their respective galaxies. They surround the outskirts of the Milky Way, where the team suspects there may be more such ancient stellar survivors.

“These older stars should be there, given what we know about galaxy formation,” says Anna Frebel, a professor of physics at MIT and part of the research. “They are part of our cosmic family tree. And now we have a new way to find them,” she adds.

As they discover similar SASS stars, the researchers hope to use them as analogs to ultrathin dwarf galaxies, which are believed to be some of the earliest surviving galaxies in the universe. These galaxies are still intact today, but they are too far away and too faint for astronomers to study in depth. Since the SASS stars may once have belonged to similarly primitive dwarf galaxies, but are in the Milky Way and, as such, much closer, they could be an accessible key to understanding the evolution of ultrathin dwarf galaxies.

“We can now look for more analogs in the Milky Way, which are much brighter, and study their chemical evolution without having to chase these extremely faint stars,” says Frebel.

The research was published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).

Excerpt from the press release published on the MIT website.

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