Undergraduate students recently discovered in data about 10 years old some of the oldest stars in the Universe in our own Milky Way.
A discovery made by “simple” students
There are approximately 13.8 billion years When the Big Bang occurred, the Universe then contained almost only hydrogen and helium which allowed the formation of the stars that we know today. However, these elements were not not the only ones present at that time, we could indeed also find traces of strontium, barium or iron.
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It is by looking for these elements that astronomers can today find the traces of the oldest stars in our Universe as was the case recently. One might believe that such a discovery would have been made by a team of experienced researchers with the help of a powerful space telescope like the famous James-Webb telescope. However, this is not the case.
Indeed, by looking for traces of the elements mentioned above, a team of MIT undergraduate students (Massachusetts Institute of Technology) succeeded in discovering three particularly old stars in our own Milky Way, having formed in the early days of our Universe ago 12 to 13 billion years.
These stars had already been observed by the Magellan telescope about ten years ago but their spectra had not yet been studied with a view to dating them, which was finally done by MIT students. However, these are located relatively “close” to Earth in our own galaxy, approximately 30,000 light years of our solar system!
Special stars that are not the only ones in our galaxy
If the discovery of such old stars is already an event in itself, the students were also able to notice other particularities concerning them. These in fact explain that these stars are animated by a retrograde movement, that is to say that they rotate in the wrong direction relative to the rest of the galactic disk. A particularity which could be highlighted by studying data from the Gaïa mission.
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This particularity could, according to the researchers, be explained by the fact that these very old stars once belonged to dwarf galaxies that encountered our Milky Way. Following this encounter, these stars were “captured” by our galaxy and continued their journey with us, while keeping this atypical rotation. This is why scientists decided to name them by the expression “ Small Accreted Stellar System » (SASS).
The student team that made this discovery, however, did not stop there. Since then, they have found traces of 65 other stars exhibiting low abundances of strontium and barium and also exhibiting retrograde motion, all located in our galaxy.
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This retrograde movement is particularly marked for the stars in question, with MIT scientists describing their movement: “ as if they were on the run “. If for the moment researchers do not know how to explain the reason for this very particular movement, the answer can surely be found in other ancient stars hiding in the Milky Way, which should now be much easier to flush out using this simple methodology, but very effective.
