The central region of the Milky Way captured by the Subaru Telescope. The image shows many stars in a field of view of about 0.4 light years. The star S0-6 (blue circle), the subject of this study, is located approximately 0.04 light years from the supermassive black hole Sagittarius A* (Sgr A*, green circle). Credit: Miyagi University of Education/NAOJ
A star near the supermassive black hole at the center of the Milky Way originated outside the galaxy, according to a new study published in Proceedings of the Japanese Academy, Series B. This is the first time that a star of extragalactic origin has been discovered near the supermassive black hole.
Many stars are observed near the supermassive black hole known as Sagittarius A*, at the center of our galaxy. But the intense gravity of the black hole makes the environment too hostile for stars to form near the black hole. Any stars observed must have formed elsewhere and migrated toward the black hole. This begs the question: where were stars formed?
Research by an international team led by Shogo Nishiyama of Miyagi University of Education indicates that some stars may come from farther away than previously thought, completely outside the Milky Way. The team used the Subaru telescope for eight years to observe the star S0-6 located just 0.04 light years from Sagittarius A*.
They determined that S0-6 is about 10 billion years old and has a chemical composition similar to stars found in small galaxies outside the Milky Way, such as the Small Magellanic Cloud and the Sagittarius dwarf galaxy.
The most likely theory to explain the composition of S0-6 is that it was born in a small, now extinct galaxy orbiting the Milky Way that was absorbed. This is the first observational evidence to suggest that some of the stars near Sagittaius A* formed outside the galaxy.
During its 10 billion year life, S0-6 had to travel more than 50,000 light years from outside the Milky Way to reach the vicinity of Sagittarius A*. It is almost certain that S0-6 traveled well over 50,000 light years, slowly spiraling down toward the center rather than making a straight shot.
Many questions remain according to Nishiyama: “Did S0-6 really originate from outside the Milky Way? Did it have companions or did it travel alone? With further investigation, we hope to break through the mysteries of stars close to the supermassive black hole.”
More information:
Shogo Nishiyama et al, Origin of a star orbiting the galactic supermassive black hole, Proceedings of the Japanese Academy, Series B (2023). DOI: 10.2183/pjab.100.007
Provided by the National Astronomical Observatory of Japan
Quote: A journey of 10 billion years and 50,000 light years towards a black hole (December 4, 2023) retrieved on December 4, 2023 from
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