Overview
- The discovery was published in Nature on Thursday, August 20, 2026, after an international team tracked the faint object first seen in 2023 and reconstructed its orbit using VLTI/GRAVITY+ data.
- Observers used the Very Large Telescope Interferometer with the upgraded GRAVITY+ instrument and new image-reconstruction techniques to detect a star about 2 billion times dimmer than Betelgeuse as seen from Earth.
- S301 completes an orbit in about 8.7 years, comes within roughly 12 astronomical units of Sagittarius A*, and reaches a peak speed of roughly 25,000 km per second, about 8% of light speed.
- Because the star moves so close and so fast, researchers say repeated, high-precision measurements—notably at its next periapse in 2031—could reveal frame-dragging from the black hole’s spin if observations cover multiple orbits over the coming decade.
- The team favors a Hills-mechanism origin in which a disrupted binary left S301 bound and may have ejected its former companion, and the result builds on decades of Galactic-center monitoring that GRAVITY+ now extends into a new, deeper regime for testing general relativity.