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Few and far between

Nature Astronomy volume 1, pages 812–813 (2017)Cite this article

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Pulsars — fast-spinning neutron stars — are precision clocks provided by nature. Finding pulsars in the Galactic Centre orbiting Sagittarius A*, the closest supermassive black hole to the Earth, will offer unprecedented opportunities to test general relativity and its alternatives.

In the fifty years since their discovery, pulsars have proven to be of tremendous value for experiments in both astrophysics and fundamental physics — from helping to understand the properties of the interstellar environment and the state of ultradense nuclear matter, to developing cosmology and testing gravity in the strong-field regime. These exciting scientific achievements have in return stimulated dozens of surveys for previously unidentified pulsars. Among these campaigns, finding pulsars at the centre of our own Galaxy, the Milky Way, would be the culmination of intensive search efforts by pulsar astronomers that have lasted for over two decades. The Galactic Centre is of particular importance because of the compelling evidence for the presence of a supermassive black hole in this region; a highly desirable companion for an orbiting pulsar. Known to astronomers by the name of its compact radio source counterpart, Sagittarius A* (Sgr A* for short), the hypothesis that it is a black hole is strongly supported by near-infrared observations. For the past two decades, monitoring of Sgr A* has revealed the rapid motion of massive stars in close orbits around an object of tremendous mass (approximately four million solar masses), but with no observable counterpart at the same wavelength1,2.

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Fig. 1: Tracking a pulsar as it orbits the central supermassive black hole.

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Acknowledgements

K.L. and R.E. acknowledge financial support by the European Research Council for the ERC Synergy Grant BlackHoleCam under contract no. 610058. Fig. 1 is based on a sketch by R.E. The telescope outline is based on a photograph by E. Middelberg.

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  1. Max Planck Institute for Radioastronomy, Bonn, Germany

    Kuo Liu & Ralph Eatough

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  1. Kuo Liu
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  2. Ralph Eatough
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Correspondence to Kuo Liu or Ralph Eatough.

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Liu, K., Eatough, R. Few and far between. Nat Astron 1, 812–813 (2017). https://doi.org/10.1038/s41550-017-0327-6

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