A faint star near the centre of the Milky Way is doing something far more interesting than lighting up a telescope image. It is tracing a path through an extreme gravitational environment—and that path could reveal how a black hole twists the space around it.
Astronomers announced S301 on 19 August 2026. It completes an orbit around Sagittarius A*, our galaxy’s central supermassive black hole, in about 8.7 years and reaches roughly 25,000 kilometres per second near its closest approach. The discovery was published in Nature. European Southern Observatory announcement
The orbit is the instrument
The black hole’s surroundings are the laboratory, but the star is the measuring tool. By tracking its motion over time, astronomers can compare the observed path with the predictions of gravity models.
The particular target here is frame dragging: the effect in general relativity by which a rotating mass influences the surrounding spacetime. Around a spinning black hole, that influence can gradually shift the orbit of a nearby star. The new paper examines how S301 could make the effect measurable. The peer-reviewed study
Picture trying to identify a very small change in the orientation of a track, rather than simply timing a runner for one lap. Speed makes S301 spectacular; a carefully measured change in its path could make it scientifically decisive.
Close to a black hole is still a vast distance
At its closest point, S301 passes around 12 times the Earth–Sun distance from Sagittarius A*. The star was found using the Very Large Telescope Interferometer in Chile, which combines observations from multiple telescopes. The team first detected it in 2023 and identified earlier observations reaching back to 2017. ESO’s discovery account
Those numbers put the work in perspective. This is not a spacecraft taking a direct reading near the black hole. It is the extraction of precise information from light arriving across the galaxy.
Nor does the discovery mean that the black hole’s spin has already been determined from this star.
The most important result is still ahead
The paper combines observations with simulations of future measurements extending to 2035. Its forecasts depend on assumptions about instrumental accuracy, observing frequency and the black hole’s spin and orientation. A simulated ability to recover a signal is a case for making the measurements—not the signal’s detection in actual future data. Study’s forecasting methods
That is why this story rewards patience. The compelling next milestone will be an increasingly constrained orbit and, ultimately, evidence for the subtle rotational effect the team wants to measure.
Our feature on time travel and what relativity actually allows explores another way that everyday intuition can fail when dealing with space and time. S301 offers something more concrete than a thought experiment: an astronomical target whose motion can be observed.
There is no need to turn the discovery into a claim that Einstein has been overturned. The remarkable possibility is that a faint, fast-moving star could help put another prediction to a demanding test.
Sometimes the best window into a black hole is not a picture of the hole itself. It is the movement of something trying to orbit it.
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