Astronomers Shocked To Discover An Extragalactic Visitor Near A Supermassive Black Hole

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According to a new study, astronomers were stunned to find a star that originated outside of the galaxy sitting near the supermassive black hole that sits at the center of the Milky Way. The find marks the first time a star of extragalactic origin has been identified so close to the supermassive black hole.

While researchers have observed stars near the supermassive black hole, known as Sagittarius A*, it is next to impossible for a star to form near the black hole itself. Until now, astronomers had believed that the stars near the black hole had all originated from within the Milky Way, which is an important distinction. However, an international team led by Shogo Nishiyama now thinks star S0-6 located only 0.3 arcseconds away from Sagittarius A* formed in another galaxy outside the Milky Way.

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Image showing the location of star S0-6 in relation to Sagittarius A*.

The team used the Subaru Telescope over the course of eight years to gather data on star S0-6. Their findings indicate that the star in question is more than 10 billion years old and is composed of chemicals similar to stars found in small galaxies outside the Milky Way. Two examples are the Small Magellanic Cloud and the Sagittarius dwarf galaxy.

Nishiyama remarked, “Did S0-6 really originate outside the Milky Way galaxy? Does it have companions, or did it travel alone? With further investigation, we hope to unravel the mysteries of stars near the supermassive black hole.”

Researchers believe the most likely theory that could explain the composition of S0-6 is that it originated in a now extinct small galaxy which orbited the Milky Way, before reaching its current residency near Sagittarius A*. The team believes the orphaned star has had to travel over 50,000 light-years.

The study, "Origin of an Orbiting Star around the Galactic Supermassive Black Hole,was published by The Japan Academy and can be viewed on the J-STAGE website.