When Galaxies Die – Stellar Stream Nyx
If there is a thing that appears almost unchanging it is the night sky. But in reality, cosmic drama takes place there and we get to see them.
Image by Lumina Obscura from Pixabay
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Now, one of these dramas was discovered by Linda Necib and her colleagues from Caltech in the data that came from the European space observatory Gaia. They discovered a stellar stream which they named Nyx – after the Greek goddess of the Night. They are convinced that this stream of stars inside our galaxy is the remains of a massive dwarf galaxy that fell victim to the Milky Way as the gravity of our galaxy tear it apart.
The space observatory is observing the Universe since 2013. It is mapping the position and movement of a large number of stars in the Milky Way. Thanks to these observations the astronomers discovered previous stellar streams which they managed to connect to other surrounding dwarf galaxies. The gravity of the Milky Way tears out stars away from them to add them to its mass.
Previous stellar streams were discovered thanks to the fact the stars in them differ in composition and how they move compared to the stars that started in the Milky Way. But if the stars of the stellar flow move consistently as the stars of our galaxy do and have a similar chemical composition then it is much harder to find them.
A bit of help from AI
That is why the scientists created an AI that analyzed the stars mapped by the Gaia observatory and searched for a grid that would correspond to a stellar flow. The AI eventually found 232 stars that move in the same direction while having a very similar chemical composition.
Following simulations of the movement of a large number of stars showed that this group of 232 stars most likely entered the Milky Way when our galaxy ate up a large dwarf galaxy. Then the researchers tracked down a similar group of stars in the Milky Way which seems to have had the same fate.
Now they hope, that further observations and analysis will give us more information about ancient galactic cannibalism.
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Interesting!