Scientists have discovered 3 of the oldest stars in the universe, 13 billion years old, on the run in the outskirts of the Milky Way Galaxy, racing in the wrong direction (retrograde motion) at hundreds of thousands of miles per hour.
Although vibrant for their age, the three stars are so old that they date back to the formation of the first galaxies, between one and two billion years after the Big Bang.
Surprisingly, they have not been observed in the far reaches of the universe by the James Webb Space Telescope. Instead, a team including undergraduates from the Massachusetts Institute of Technology (MIT) found it in archival data.
Scientists discovered these stars, which they called SASS, an abbreviation for Small Accreted Stellar System, in the Milky Way's halo, a diffuse cloud of stars, gas, and dust that envelops our entire galaxy.
Based on their analyses, scientists believe that these stars were formed between 12 and 13 billion years ago, that is, at the time when the first galaxies were formed, which are 13.8 billion years old.
Its age means it provides a completely new avenue for scientific research, and could shed light on the evolution of some early galaxies.
MIT scientists called the stars “small stars accreting into a star system (SASS)” because they believe each one once belonged to a small, primitive galaxy.
It is possible that these host galaxies were eventually absorbed by the Milky Way, which is known to have swallowed entire galaxies throughout its existence.
Essentially, these stars are the remains of ancient galaxies orbiting the edges of the Milky Way. There may be a lot of other information that has not yet been discovered.
“These oldest stars must certainly exist, given what we know about galaxy formation,” Anna Friebel, a physics professor at MIT, explained in a press release. “They are part of our cosmic family tree.” “We now have a new way to find them,” she added.
The new stars were discovered during a study project at the Massachusetts Institute of Technology called 8.S30 under the supervision of Dr. Frebel, which began in the fall of 2022.
The students were tasked with learning ancient star analysis techniques and then applying them to stars that had never been examined before. They combed through archival star data from the 6.5-meter Magellan-Clay telescope at Las Campanas Observatory.
The team of scientists now aims to detect more similar SASS stars. By doing so, they believe they can shed new light on faint dwarf galaxies.
Although SASS stars now form part of the Milky Way, they previously belonged to primitive dwarf galaxies. As such, it can teach scientists a lot about the evolution of extremely faint dwarf galaxies, which are believed to be one of the oldest galaxies in the universe, but whose dimness makes them undetectable.
“Now we can search for more analogues in the Milky Way, which are much brighter, and study their chemical evolution without having to chase these very faint stars,” Friebel said in an MIT statement.
The origin of the stars as part of the galaxies being devoured by the Milky Way has been revealed not only by their metal-poor compositions, but also by the fact that they rotate in a different direction from the main disk of the Milky Way, and most of its halo. The stars also showed random angles and strange paths that persisted for billions of years.
“They are running away,” Friebel explains. “Interestingly, they are all very fast - hundreds of kilometers per second - and are moving in retrograde motion (which is the orbital or rotational movement of an object in the opposite direction of rotation of its primary body, which forms the central body). We do not know why this happens.” .
The scientists published details of their findings in a new paper in the journal Monthly Notices of the Royal Astronomical Society.
It is interesting to learn about faint dwarf galaxies
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