X-ray light curve of Sgr A* over the past 250 years. The green points at L_X ~ 10³⁹ erg s^-1 show the constraints on the Sgr A* activity inferred from the Fe-Kα measurements in the Sgr B2 cloud (see text, Inui et al. 2009; Terrier et al. 2010). The red points show the current quiescence level of Sgr A*, together with the brightest flare ever measured (Porquet et al. 2003, P03). The blue points in the box show the results of this work.