By TETSUYA ISHIKURA/ Staff Writer
January 9, 2024 at 08:00 JST
The fixed star S0-6 likely relocated from outside the galaxy to an area in close proximity to the black hole Sagittarius A*, pronounced “Sagittarius A star,” at the center of the Milky Way galaxy. This image was taken with the Subaru Telescope. ((C) the Miyagi University of Education/ the National Astronomical Observatory of Japan)
Astronomers were astounded to discover that a fixed star near the massive black hole at the center of the Milky Way originated in another galaxy.
The observation made using the Subaru Telescope by a team of researchers primarily from the Miyagi University of Education and the National Astronomical Observatory of Japan marks the first discovery of such an inter-galaxy star.
“I was really stunned” by the outcome, said Shogo Nishiyama, an associate professor of astronomy at the Miyagi University of Education.
A supermassive black hole exists at the core of the Milky Way galaxy, of which the solar system that comprises Earth and the other planets is a part. It is called Sagittarius A*, pronounced “Sagittarius A star.”
As the origins of stars whizzing around the black hole remained unclear, Nishiyama and his colleagues examined the fixed star S0-6 in proximity to the black hole for a prolonged period.
The results showed S0-6 sits within 0.6 light-years, or 6 trillion kilometers, of the black hole. The distance is equivalent to the size of the solar system, meaning S0-6 is under the influence of the huge black hole 4 million times the mass of our sun.
Studying the brightness level and temperature of the star revealed S0-6 was formed 10 billion years ago and has a similar elemental composition to that of stars in the Small Magellanic Cloud and the Sagittarius dwarf galaxy near the Milky Way galaxy.
All those factors indicate S0-6 may have been born outside the Milky Way galaxy and that it traveled more than 50,000 light-years to the center of the Milky Way galaxy over the course of 10 billion years.
Of numerous fixed stars around the black hole, around 10 were examined during the study. S0-6 was the sole body considered to have come from another galaxy.
“We will be unlocking mysteries concerning stars around the black hole, such as whether it (S0-6) had a companion, in the hope of determining if it reached there alone,” said Nishiyama.
Nishiyama said he intends to continue to monitor those stars on a continual basis.
The team’s findings were published in the Japan Academy’s bulletin at (https://doi.org/10.2183/pjab.100.007) on Dec. 1.
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