天文学：天の川銀河のブラックホールの自転を感じとる恒星

A star that appears to be sensitive to the spin of the supermassive black hole at the centre of the Milky Way is reported in Nature this week. This discovery could enable researchers to more closely analyse the spin of supermassive black holes, although more research is needed to fully assess the star’s potential.

Black holes have three primary properties which can vary between them; mass, charge, and spin. Although spin estimates have been obtained through X-ray observations, it has never been possible to directly measure the spin of a black hole due to challenges associated with collecting these measurements.

The GRAVITY+ Collaboration report the discovery of a main-sequence star orbiting Sagittarius A* (the closest supermassive black hole to Earth, found at the centre of the Milky Way). Measurements from the European Southern Observatory’s Very Large Telescope Interferometer suggest that the star’s motion is sensitive to the spin of the black hole. The star, named S301, has an 8.7-year orbit around the black hole (the shortest known orbital period around Sagittarius A*) and at its nearest approach is just approximately 1.7 billion kilometres away from it. S301 is ten times closer to Sagittarius A* than the next nearest test star for assessing the black hole and thus a hundred times more sensitive to its gravitational field. Although the direct measurement of the black hole’s spin cannot be determined by these observations alone, they could provide a practical route to obtaining this measurement in future research.

• Article
• Open access
• Published: 19 August 2026

Abd El Dayem, K., Abuter, R., Aimar, N. et al. Discovery of a star sensitive to the spin of Sagittarius A*. Nature (2026). https://doi.org/10.1038/s41586-026-10894-w

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