New Star Discovered Orbiting Sagittarius A*
The star S301 completes a full orbit in 8.7 years, offering a new method to measure the black hole's spin.
Updated on Oct. 21, 2026 in Space
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Astronomers have identified a star, S301, with an 8.7-year orbit around the Milky Way's central black hole, Sagittarius A*. This discovery, published in Nature on August 19, 2026, marks the shortest known orbital period for a star around this black hole.
Why it matters
By tracking the tight orbit of S301, researchers aim to quantify the spin of Sagittarius A* using the gravitational phenomenon of frame dragging. This measurement is essential for understanding how the massive black hole influences the galactic center.
S301 is a star with 1.5 solar masses that reaches a minimum proximity of 1.1 billion miles from the 4.3-million-solar-mass black hole. Observations were derived using the GRAVITY instrument on the Very Large Telescope Interferometer and the GRAVITY-RESOLVE processing code.
The players
Max Planck Institute
A German research organization conducting high-precision astrophysical observations and galactic center dynamics.
Very Large Telescope Interferometer
An optical interferometer located at the Paranal Observatory that enables high-resolution imaging of stellar orbits.
The details
Astronomers utilized the GRAVITY instrument, an interferometric tool that combines light from multiple telescopes to achieve high angular resolution, to isolate the star from the dense galactic center. The team applied the GRAVITY-RESOLVE imaging code to reconstruct the star's trajectory from raw interference data. This proximity creates a gravitational environment sensitive enough to reveal frame dragging—a process where a rotating massive object drags the fabric of spacetime around it.
Timeline
March 2017: S301 is captured in archival exposures.
Spring 2023: Researchers first identify the star.
August 19, 2026: The research findings are published in Nature.
2031: The star is scheduled for its next swing past the black hole.
The Tech Race
This discovery extends the ongoing GRAVITY observation program at the galactic center by providing a more precise probe of spacetime near Sagittarius A*. It sets a new benchmark for measuring orbital velocity in the extreme gravitational field of the Milky Way.
There are no immediate consumer applications, as this research focuses on fundamental astrophysical measurements of galactic dynamics. Astronomers expect the next orbital pass of S301 in 2031 to provide the data required to finalize the spin measurement of the black hole.
The takeaway
The study establishes S301 as the most precise tool currently available for probing the gravitational influence of our galaxy's central black hole. Watch for future imaging data when the Extremely Large Telescope begins operations to confirm the spin parameters of Sagittarius A*.
What happens next
The research team plans to utilize the MICADO instrument on the upcoming Extremely Large Telescope to map the orbit in three dimensions within the next four years.
Further reading
For more on recent developments in cosmic monitoring, see our section on Space.
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