• Mar 05 2015

    Article has appeared Physical Review Letters (PRL)

    Orbital Resonances around Black Holes


    Resonance effects are ubiquitous to multi-frequency systems - they have sculpted Saturn’s rings and the gaps in the asteroid belt and are harbingers of dynamical chaos. A unique feature of dynamics in general relativity is the existence of three orbital frequencies. As a result, orbits near black holes can exhibit intriguing resonant phenomena.

    Resonant effects around black holes will potentially be observable with the Event Horizon Telescope, eLISA, X-ray missions and the Square Kilometer Array. To facilitate these observations physicists from South Africa and the United States have comprehensively characterized the associated time and length scales for spinning black holes.

    The supermassive black hole, SgrA*, at our Galactic Centre provides an exciting laboratory for observing a number of strong field orbital effects. The authors show that the impact of resonances will dominate within 50 Schwarzschild radii of the black hole. A neutron star in this region will traverse all the resonance bands (depicted in the figure), resulting in phase shifts in the gravitational wave emission. Measuring hourly fluctuations in the radio emission or resolving horizon scale phenomena around SgrA* can probe the potential formation of a resonant ring structure. Outside the strong resonance region, the long term timing of a pulsar could lead to the first measurement of the black hole’s quadrupole moment free of chaotic effects.


    Written by
    Marisa Geyer
    SKA Radio Astronomy

    Article can be found here:
    http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.081102

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