Accretion disk
Hot gas swirls in an accretion flow, as it is gradually sucked into the supermassive black hole at the centre of our galaxy. The energy of the gas is converted into radiation,which is emitted in sudden bursts. Genzel et al have detected several flares of radiation at infrared wavelengths, which may result from the emission of blobs of gas from the disk (accompanied by
radiation) or from sparks that occur randomly in the accreting gas. The inset shows the earlier,
similar detection of an X-ray flare. Piecing together observations of the black hole across a range
of wavelengths should reveal the complex physical processes that occur in accretion flows. (Image and text courtesy of Nature 425 908 - based on an image created by Michael P Owen.)