Simultaneous X-ray and infrared observations of the galactic center
The supermassive black hole (SMBH) at the center of our Milky Way galaxy, Sagittarius A*, is by far the closest such object to us, only about 25 thousand light-years away. Although not nearly as active or luminous as other SMBHs, its relative proximity provides astronomers with a unique opportunity to probe what happens close to the "edge" of a black hole. Monitored in the radio since its discovery and more recently in the infrared and the X-ray, Sgr A* appears to be accreting material at a very low rate, only a few hundredths of an Earth-mass per year. Its X-ray emission is persistent, probably resulting from the rapid motions of electrons in the hot accretion flow associated with the black hole. Once a day there are also flares of emission that are highly variable; they appear more often in the infrared than in X-rays. Some submillimeter wavelength flares have also...