Discovery of a star sensitive to the spin of Sagittarius A.

Residing in the centre of the Milky Way, Sagittarius A* (Sgr A*) is the closest massive black hole 1 (MBH).

Residing in the centre of the Milky Way, Sagittarius A* (Sgr A*) is the closest massive black hole 1 (MBH). Its vicinity has allowed measuring individual stellar orbits around it 2-4 . The stars act as test particles and probe the gravitational potential around the 4.3 × 10 6 M…