26 / A star near the edge
The Orbit That Could Reveal a Black Hole's Spin
S301 circles the Milky Way's central black hole on an unusually tight, elongated path. Repeated measurements may expose the subtler effect of the black hole's rotation.
A star can serve as a test particle when its orbit passes through strong gravity and survives to return. The newly reported S301 completes a circuit around Sagittarius A* in about 8.7 years and reaches an extreme speed near closest approach. Researchers propose that future astrometry and spectroscopy could distinguish the small orbital changes associated with spin from the already measured effects of mass and ordinary relativistic precession. Its stretched orbit also suggests a violent origin: a binary pair may have been torn apart, leaving one member bound.
The full investigation continues with the evidence, illustrations, and sources at The Last Transmission on Substack.
Continue reading on SubstackTHE EVIDENCE / THE OPEN QUESTION
What we know.
Near-infrared interferometry has identified S301 and constrained its orbit close to the roughly four-million-solar-mass black hole. Its peak speed is reported near 25,000 kilometers per second, making relativistic effects potentially accessible to future measurements.
What remains open.
The black hole's spin has not been read from S301's orbit yet. The proposed binary-disruption history is an inference from its eccentricity; the former partner has not been identified. Repeated observations must separate subtle relativistic signatures from other influences.
Why it matters.
The same star can become a long-running experiment in gravity. Each return offers another chance to test how a rotating black hole changes the space through which an ordinary object moves.
GO DEEPER / EVIDENCE FILE
Can S301 Measure Our Black Hole's Spin?
GRAVITY tracked S301 and fit an 8.7-year orbit. The subtle spin-related change remains a forecast that future astrometry and spectroscopy must separate from other pulls.
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