Three oldest stars in the Universe turned out to be neighbors of the Earth: how they were found

A team of MIT researchers has discovered three of the oldest stars in the Universe. They could have been formed between 12 and 13 billion years ago, which is when the first galaxies were born.

The stars are located on the outskirts of the Milky Way, and even the James Webb Space Telescope has not seen them, writes Interesting Inginering. Their age opens up a completely new path for scientific research into the evolution of the oldest galaxies.

Ancient galactic remnants

Scientists named the stars "SASS", which means "Small Accreted Stellar System". Researchers believe that each of them once belonged to a small primitive galaxy.

These galaxies were later absorbed by the Milky Way. It is known that during its existence, it completely absorbed smaller galaxies.

In fact, these stars are the remnants of ancient galaxies that surround the outskirts of the Milky Way. And there may be many others that have yet to be discovered.

"These oldest stars should definitely be there, given what we know about galaxy formation. They are part of our cosmic family tree. And now we have a new way to find them," said physics professor Anna Froebel.

The discovery of the new stars took place during a project at MIT. During the fall semester of 2022, Froebel started a new course called 8.S30 (Observational Stellar Archaeology).

The students were tasked with learning methods for analyzing ancient stars and then applying them to stars that had never been studied before. They examined archival data on stars from the 6.5-meter Magellanic Clay Telescope at Las Campanas Observatory.

"Although most of our classes are taught from scratch, this course immediately put us on the cutting edge of astrophysics research," said Hillary Andales, co-author of the study.

SASS stars as analogs of ultra-faint dwarf galaxies

The team of scientists is now seeking to identify more similar SASS stars. This should provide more information about ultra-faint dwarf galaxies.

It is to such primitive galaxies that SASS once belonged, which are now part of the Milky Way.

This means that the newly discovered old stars can tell us a lot about the evolution of ultra-faint dwarf galaxies. These are believed to be some of the oldest galaxies in the Universe, but they are usually too faint to detect.

Since the SASS stars are close to our galaxy, they are much easier to observe with existing instruments.

"We can now look for more counterparts in the Milky Way that are much brighter and study their chemical evolution without having to chase these extremely dim stars," Froebel said.

The researchers described their findings in detail in a new article in the Monthly Notices of the Royal Astronomical Society.

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