Implication of spin constraints by the Event Horizon Telescope on stellar orbits in the Galactic Center

Understand

The center of the Milky Way hosts the closest supermassive black hole, SgrA$^*$.

• Decades of near-infrared observations of our Galactic Center have shown the presence of a small population of stars (the so called S-star cluster) orbiting SgrA$^*$, which were recently reported to be arranged in two orthogonal disks.
• In this case, the timescale for Lense-Thirring precession of S-stars should be longer than their age, implying a low spin for SgrA$^*$.
• In contrast, the recent results by the Event Horizon Telescope favor a highly-spinning SgrA$^*$, which seem to suggest that the S-stars could not be arranged in disks.