Scientists may have discovered an extragalactic guest among the stars orbiting the supermassive black hole at the centre of our Milky Way, Sagittarius A*, or Sgr A*.
Sgr A* is surrounded by many stars, whose fast orbits helped astronomers determine that the mass of the black hole is about 4.5 million times greater than the mass of the Sun. However, as useful as these stars are, their existence is somewhat mysterious. This is because the intense gravity of Sgr A* should make the heart of the Milky Way an environment that is too turbulent for star formation. This led scientists to theorize that the stars around Sgr A* could have migrated to this region after being born in another corner of the universe.
New data from an international team of scientists has shown that some of these stars may have travelled much longer to Sgr A* than previously thought. Specifically, the team found that the star, designated “S0-6,” may be more than 10 billion years old and may have formed about 50,000 light-years from its current location.
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To confirm the extragalactic origin of S0-6, scientists studied the star for eight years using the 8.2-meter Subaru Optical-Infrared Telescope, located near the summit of Mauna Kea in Hawaii. The study found that the star, visible only 0.3 arcsec from Sgr A*, is chemically similar to stars found in the Milky Way’s small satellite galaxies, such as the Small Magellanic Cloud and the Sagittarius dwarf galaxy.
So scientists hypothesized that S0-6 was born in a small companion galaxy to the Milky Way that was absorbed by our galaxy at some point in the last 10 billion years. This would cause the star to travel tens of thousands of light-years to Sgr A* and spiral around the black hole at the centre of the galaxy.
If all this is confirmed, S0-6 will be the first extragalactic star discovered near Sgr A*. But many questions will remain about the existence of this star and the history of all other stars living on the edge of a supermassive black hole. Did S0-6 originate outside the Milky Way galaxy? Does she have companions, or did she travel alone? – think scientists. “With the help of further research, we hope to unravel the mysteries of the stars near the supermassive black hole.”
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