A star has been found orbiting closer than any known star around the supermassive black hole at the center of our galaxy, "Sagittarius A*," and moving the fastest in the Milky Way.
The "GRAVITY+ collaboration," which includes the Max Planck Institute for Extraterrestrial Physics (MPE) in Germany, announced on the 20th in the international journal Nature that it discovered the star "S301" using the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO).
S301 is a main-sequence star with a mass similar to the sun's, orbiting Sagittarius A* once about every 8.7 years. Its orbit is highly elongated, narrowing to about 12 times the Earth-sun distance at closest approach to the black hole. At that point, its speed is about 25,000 km per second, exceeding 8% of the speed of light. This is the fastest among stars confirmed so far in the Milky Way.
The researchers see a low likelihood that S301 formed where it is now. A leading scenario is the "Hills mechanism," in which a binary star system approached Sagittarius A*, was split by strong gravity so that one star was ejected while S301 was captured by the black hole.
Another reason the discovery is drawing attention is that it could provide a new way to measure the spin of Sagittarius A*. According to general relativity, a rotating black hole induces "frame dragging," which pulls the surrounding spacetime and leaves subtle changes in the orbits of nearby stars.
Because S301 is extremely close to the black hole and moves quickly, it is well suited for observing such effects. The team said that by precisely tracking S301's position and velocity, it may be possible within about 10 years to measure how the spin of Sagittarius A* affects the star's orbit.
Stefan Gillessen of MPE said, "If we observe objects like S301 over a long period, we can directly infer the spin of Sagittarius A* and use it to test Einstein's general relativity in a strong-gravity environment."
References
Nature (2026), DOI: https://doi.org/10.1038/s41586-026-10894-w