A 10-billion-year, 50,000-light-year journey to a black hole

According to a recent research published in Proceedings of the Japan Academy, Series B, a star close to the supermassive black hole at the heart of the Milky Way galaxy originated outside the galaxy. This is the first time a star outside of our galaxy has been discovered close to a supermassive black hole.

Sagittarius A*, the supermassive black hole in our galaxy's center, is observed to be close to a large number of stars. However, the surrounding environment is too hostile for stars to develop close to the black hole due to its strong gravity. Every star that has been seen had to have developed someplace else and moved in the direction of the black hole. The issue of where the stars formed is raised by this.

According to research conducted by a multinational team under the direction of Shogo Nishiyama at Miyagi University of Education, certain stars may have originated from sources beyond the Milky Way entirely, which is farther distant than previously believed. Over the course of eight years, the researchers observed the star S0-6, which is just 0.04 light-years distant from Sagittarius A*, using the Subaru Telescope.

They discovered that S0-6 is around 10 billion years old and that its chemical makeup is comparable to that of stars in dwarf galaxies in Sagittarius and the Small Magellanic Cloud, two galaxies outside of the Milky Way.

The most plausible explanation for S0-6's composition is that it originated in a tiny galaxy that is now extinct and was swallowed by the Milky Way when it was orbiting the galaxy. This is the first empirical evidence that points to some of the nearby stars of Sagittaius A* as having originated outside of the galaxy.

S0-6 had to have traveled more than 50,000 light-years from beyond the Milky Way to get to the area around Sagittarius A* over its 10 billion-year existence. S0-6 most likely traveled about 50,000 light-years, descending slowly in a spiral fashion to the center rather than in a straight line.

Nishiyama claims that many questions remain. "Did S0-6 indeed come from a galaxy other than our own? Was it traveling with other people or by itself? We want to solve the mystery surrounding the stars close to the supermassive black hole with more research."