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Astrophysics

Bringing black holes into focus

Nature volume 455, pages 39–40 (2008)Cite this article

Do black holes exist? Observations at the finest resolution so far indicate that only gross deviations in the behaviour of gravity from that predicted by general relativity can invalidate the case that they do.

On page 78 of this issue, Doeleman et al.1 report new observations of Sagittarius A* (Sgr A*), the enigmatic source of radio waves at the centre of our Galaxy2 that has long been suspected as signposting our very own supermassive black hole. These new data have allowed the authors, for the first time, to detect structure in the radio emissions from Sgr A* on scales as small as 50 million kilometres. The diameter of our Galaxy's black hole (which has a mass 4 million times that of the Sun) is expected to be approximately 12 million to 24 million kilometres. But the strong bending of light rays within the gravitational field of the black hole will double the apparent size of the event horizon, the boundary of the area around the black hole from which nothing, not even light, can escape. Thus Doeleman and colleagues' observations have finally brought us to the threshold of imaging horizon-scale structures — a holy grail of radio astronomy.

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  1. Christopher S. Reynolds is in the Department of Astronomy, University of Maryland, College Park, Maryland 20742, USA. chris@astro.umd.edu,

    Christopher S. Reynolds

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  1. Christopher S. Reynolds
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Reynolds, C. Bringing black holes into focus. Nature 455, 39–40 (2008). https://doi.org/10.1038/455039a

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