Black Hole Shadows
10 April 2019Black holes are a fundamental result of Einstein’s theory of General Relativity, and all sufficiently massive stars are expected to eventually turn into black holes. However, while theoretically very well established, we had yet to directly see a black hole. Until now. Today, the Event Horizon Telescope (EHT) collaboration  revealed the world’s first image of a supermassive black hole, residing at the core of our galactic neighbour M87.
This amazing image, taken at radio wavelengths by a globe-spanning network of radio telescopes, shows a distorted picture of the M87 core, painted by the light emitted from hot plasma in the region. The distortion is caused by the strong gravitational field in the area, strong enough to bend the path of light itself. The precise nature of the distortion, or gravitational lensing, is like a fingerprint of the type of exotic object lurking there. In particular, the silhouette, or ‘shadow’, in the EHT image is evidence that this object is indeed a black hole, which is absorbing some of the light emitted by the plasma before it can reach us.
ESA’s Advanced Concepts Team has been studying the precise shape of these shadows, and their sensitivity to different theoretical models of gravity. This allows us to use the EHT as a probe - one of the few we have - to test our understanding of gravity in its most extreme regime. We perform this analysis through simulations of the gravitational lensing process, with results such as [I,II,III].
ESA is also working on boosting the resolution of the EHT by taking it into space . A space based EHT using Earth orbiting satellites could be capable of resolving even the fine details of the black hole to a level unachievable by purely Earth based observations.
Experience the gravitational lensing caused by different models of gravity for yourself by heading over to our black hole lensing website visualising the results of this research.
- Event Horizon Telescope
- Martin-Neira, M., V. Kudriashov, I. Barat, B. Duesmann, E. Daganzo, P. Martin-Iglesias, N. Alagha, et al. 2017. “Space-Borne Radio Telescope to Image the Supermassive Black Hole at Our Galactic Centre.” In in Proceedings of the 38th ESA Antenna Workshop, ESA/ESTEC, Netherlands
Grover, J., J. Kunz, P. Nedkova, A. Wittig, and S. Yazadjiev. 2018. “Multiple Shadows from Distorted Static Black Holes.” Phys. Rev. D 97 (8): 084024. [link]
Grover, J., and A. Wittig. 2017. “Black Hole Shadows and Invariant Phase Space Structures.” Phys. Rev. D 96 (024045). [link]
Cunha, P. V. P., J. Grover, C. Herdeiro, E. Radu, H. Runarsson, and A. Wittig. 2016. “Chaotic Lensing around Boson Stars and Kerr Black Holes with Scalar Hair.” Phys. Rev. D 94 (10): 104023. [link]