SpaceTime

Image: This artist's impression illustrates how high-speed jets from supermassive black holes would look. These outflows of plasma are the result of the extraction of energy from a supermassive black hole’s rotation as it consumes the disc of swirling material that surrounds it. Credit: NASA, ESA, M. Chiaberge (STScI) The radiation from an active galactic nuclei (AGN) is believed to be a result of accretion of mass by a supermassive black hole at the centre of its host galaxy. In a recent paper (Hirotani et al., 2016 ApJ) the authors demonstrate that electrons and positrons created by photon collisions near a rotating black hole are accelerated in the opposite direction by the electric field present near the event horizon. This electric field acts as a particle accelerator (or gap) and dissipates a part of the hole’s rotational energy. The resultant gamma-ray luminosity increases with decreasing plasma accretion from the surroundings. The authors show that in the case o...

Image: Artistic illustration of a black hole divouring a star. Credit: NASA/Goddard Space Flight Center/CI Lab   A tidal disruption event occurs when a star gets close enough to a supermassive black hole's event horizon and is pulled apart by the black hole's tidal forces.

Image: Anatomy of the Sun. Credit: NASA/Jenny Mottar The standard model of solar flares explains many observational features of flares, assuming that they are driven by magnetic reconnection. F lares release approximately 10 30 –10 33 erg into the plasma but it is not clear, however, how that energy is partitioned between in situ heating of the corona, particle acceleration, and wave generation, nor to what extent the observable features of a flare depend on the balance between different types of coronal energy transport.

Image: Combined HST and Chnadra imaging of the supernova remnant SNR 0509-67.5 in the LMC To find distances in space, astronomers use objects called "standard candles", objects that give a certain, known amount of light. Because astronomers know how bright these objects truly are, they can measure their distance from us by analyzing how dim they appear.

Supermassive black holes at the cores of galaxies blast radiation and ultra-fast winds outward, as illustrated in this artist's conception. Credit: NASA/JPL-Caltech Broad emission lines are a hallmark feature of type 1 active galactic nuclei (AGNs) and quasars. Many basic properties of the broad-line region (BLR), such as its basic geometry, dynamics, and physical connection to the accretion disk around the supermassive black hole (BH), remain illdefined. AGN spectra exhibit both tremendous diversity as well as discernable patterns of systematic regularity.

Image: Colour composite image of Centaurus A, revealing the lobes and jets emanating from the active galaxy’s central black hole. This is a composite of images obtained with three instruments, operating at very different wavelengths. The 870-micron submillimetre data, from LABOCA on APEX, are shown in orange. X-ray data from the Chandra X-ray Observatory are shown in blue. Visible light data from the Wide Field Imager (WFI) on the MPG/ESO 2.2 m telescope located at La Silla, Chile, show the background stars and the galaxy’s characteristic dust lane in close to "true colour". Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray) A maser, an acronym for 'microwave amplification by stimulated emission of radiation', is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The maser was the forerunner of the laser: they work by the same principle. The difference is...