The star near Sagittarius A* with an orbit of about 16 years is S2.
Also called S0–2, S2 is a young, massive B-type star orbiting the supermassive black hole at the center of the Milky Way. Its measured orbital period is about 16.05 years, and its highly eccentric path brings it to within roughly 17 light-hours of Sagittarius A*, or about 120 astronomical units.
S2 is valuable because its motion lets astronomers measure the mass of the central object and test Einstein’s general relativity in an extreme gravitational environment. During its close passage in 2018, observations detected the predicted gravitational redshift of its light, providing a striking confirmation of relativistic effects near the Galactic Center.
The star should not be confused with S0–102, another closely tracked Galactic Center star whose orbital period is about 12.8 years. S2 is also not the black hole itself: it is a luminous orbiting star, while Sagittarius A* is the compact radio source associated with the central black hole.