Today's Colloquium: BlackHoleCam: Zooming in onto the Galactic Center Black Hole

© Heino Flacke

Black holes are supposed to power the nuclei of galaxies. The best place to test this paradigm is the Galactic center. Here a compact radio source, Sgr A*, with a mass of 4 Million solar masses marks the very center of our Galaxy. Numerical magnetohydrodynamic simulations and semi-analytic models seem to converge towards a combined jet-disk model producing radiation from radio to X-rays to explain the emission. Interestingly, radio interferometry and timing observations are now probing the smallest scales of this object, directly confirming that the high-frequency radio emission indeed comes from event-horizon scales. This allows one to study basic astrophysical processes such as jet formation and accretion physics. Precise measurements of NIR-emitting stars and potentially even radio pulsars in the Galactic Center help us to constrain mass and possibly spin of the black hole reliably. Using future mm-VLBI experiments it should be possible to even image the elusive event horizon of a black hole for the very first time. All this we address within the framework of a new ERC-funded project, BlackHoleCam, which seeks to turn Sgr A* into a fundamental laboratory for precision black hole astrophysics.