Because of the very definition of black holes — no light escapes them and falling objects get infinitely faint when approaching — it is impossible to ever prove that they exist. However, electromagnetic and gravitational-wave observatories have now ‘seen’ black holes. Datasets from these observations, released in late 2018 and 2019, give important hints about the environment, origin and growth of black holes.
GRAVITY combines four telescopes to form the equivalent of a telescope of 130 m diameter. It has observed luminous material extremely close to the black hole at the centre of our galaxy.
The Event Horizon Telescope combines radio telescopes in different continents, equivalent to a detector as big as our planet. This has been used to observe the surroundings of the black hole at the centre of the Messier 87 galaxy, revealing a dark core surrounded by a luminous halo.
The latest full LIGO–Virgo data release contains 11 events, 10 of which involve black holes.
All observations are consistent with general relativity and predictions for black holes, but the coming years will bring more insights.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $8.67 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Reall, H. Viewpoint: A possible failure of determinism in general relativity. Physics 11, 6 (2018).
Luminet, J.-P. An illustrated history of black hole imaging: personal recollections (1972–2002). Preprint at arXiv https://arxiv.org/abs/1902.11196 (2019).
Akiyama, K. et al. First M87 event horizon telescope results. I. The shadow of the supermassive black hole. Astrophys. J. 875, L1 (2019).
Abuter, R. et al. Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*. Astron. Astrophys. 618, L10 (2018).
Cardoso, V. & Pani, P. Testing the nature of dark compact objects: a status report. Living Rev. Relativ. 22, 4 (2019).
Chen, Y., Shu, J., Xue, X., Yuan, Q. & Zhao, Y. Probing axions with event horizon telescope polarimetric measurements. Preprint at arXiv https://arxiv.org/abs/1905.02213 (2019).
Davoudiasl, H. & Denton, P. B. Ultralight boson dark matter and event horizon telescope observations of M87*. Phys. Rev. Lett. 123, 021102 (2019).
Bar, N., Blum, K., Lacroix, T. & Panci, P. Looking for ultralight dark matter near supermassive black holes. J. Cosmol. Astropart. Phys. 2019, 045 (2019).
Abbott, B. P. et al. GWTC-1: a gravitational-wave transient catalog of compact binary mergers observed by LIGO and Virgo during the first and second observing runs. Phys. Rev. X 9, no. 3, 031040 (2019).
Compère, G. Are quantum corrections on horizon scale physically motivated? Preprint at arXiv https://arxiv.org/abs/1902.04504 (2019).
The author is grateful to Ana Sousa for the image and is indebted to E. Berti, P. Cunha, K. Destounis, F. Eisenhauer, M. C. Ferreira, J. Grover, C. Herdeiro, D. Hilditch, J. P. S. Lemos and F. Vincent for important feedback.
The author declares no competing interests.
Gravitational Wave Events application: https://apps.apple.com/us/app/gravitational-wave-events/id1441897107
ESA ACT BH visualization tool: https://www.esa.int/gsp/ACT/phy/Projects/Blackholes/WebGL.html