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The Milky Way Stole Some of its Stars from Another Galaxy

Milky Way

An intriguing fact that has been discovered in the past decade is that at least half of the 11 most distant stars in our galaxy are far from the spiral disk of our Milky Way.

These celestial bodies are about 300 000 light-years from Earth. Scientists now explain this inconsistency with the theory that these stars don't belong to our galaxy at all. They were simply snatched from a neighboring one thanks to the unimaginable gravity of the Milky Way.

The theory comes from a group of astronomers from Harvard University. They posit that these stars are part of a slow but constant stream of cosmic material ejected from the dwarf galaxy Sagittarius. It is one of the many mini galaxies situated near the Milky Way that get closer to it with each full orbit they complete.

Their hypothesis states that the stars were stolen from the dwarf galaxy Sagittarius, which neighbors our own Milky Way. To prove this, the scientists have come up with a model to recreate the path traveled by Sagittarius over the last 8 billion years. They used astronomical observations in order to simulate the speed and movement of the galaxy.

"The initial speed and angle of approach greatly affect the orbit, just like the speed of a rocket and the angle it's launched from affect its trajectory, " stated Avi Loeb from the University.


According to the model, about 8 billion years ago, the mini galaxy came exceptionally close to the Milky Way. Since Sagittarius has significantly less gravity, our galaxy captured nearly 1/3 of its stars and 90% of its dark matter.

The model illustrated that 3 streams of stars from the dwarf galaxy Sagittarius began their course toward the center of the Milky Way, crossing a distance of over 1 million light-years. The new finds were made possible thanks to the data collected from the Sloan Digital Sky Survey in New Mexico.

The information has helped scientists identify the 5 stars believed to be a small part of the stolen material in the Milky Way. Scientists are hoping they'll find even larger structures, predicted by their models.