Shen, Zhi-Qiang and Lo, K. Y. and Liang, M. C. and Ho, Paul T. P. and Zhao, J.-H. (2005) A size of ~1 AU for the radio source Sgr A* at the centre of the Milky Way. Nature, 438 (7064). pp. 62-64. ISSN 0028-0836. https://resolver.caltech.edu/CaltechAUTHORS:20150330-090926147
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Abstract
Although it is widely accepted that most galaxies have supermassive black holes at their centres, concrete proof has proved elusive. Sagittarius A* (Sgr A*), an extremely compact radio source at the centre of our Galaxy, is the best candidate for proof, because it is the closest. Previous very-long-baseline interferometry observations (at 7 mm wavelength) reported that Sgr A* is ~2 astronomical units (au) in size, but this is still larger than the 'shadow' (a remarkably dim inner region encircled by a bright ring) that should arise from general relativistic effects near the event horizon of the black hole. Moreover, the measured size is wavelength dependent. Here we report a radio image of Sgr A* at a wavelength of 3.5 mm, demonstrating that its size is ~1 au. When combined with the lower limit on its mass11, the lower limit on the mass density is 6.5 × 10^21 M_⊙ pc^-3 (where M_⊙ is the solar mass), which provides strong evidence that Sgr A* is a supermassive black hole. The power-law relationship between wavelength and intrinsic size (size proportional to wavelength^1.09) explicitly rules out explanations other than those emission models with stratified structure, which predict a smaller emitting region observed at a shorter radio wavelength.
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Additional Information: | © 2005 Nature Publishing Group. Received 1 July; accepted 31 August 2005. The Very Large Array and the Very Long Baseline Array are operated by the National Radio Astronomy Observatory, which is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities Inc. Z.-Q.S. acknowledges support from the One-Hundred-Talent programme of the Chinese Academy of Sciences. | ||||||||||||||||||
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Issue or Number: | 7064 | ||||||||||||||||||
Record Number: | CaltechAUTHORS:20150330-090926147 | ||||||||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20150330-090926147 | ||||||||||||||||||
Official Citation: | Shen, Z.-Q., Lo, K. Y., Liang, M. C., Ho, P. T. P., & Zhao, J. H. (2005). A size of [sim]1[thinsp]au for the radio source Sgr A[ast] at the centre of the Milky Way. [10.1038/nature04205]. Nature, 438(7064), 62-64. | ||||||||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||||||||
ID Code: | 56202 | ||||||||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||||||||
Deposited By: | Jason Perez | ||||||||||||||||||
Deposited On: | 30 Mar 2015 23:58 | ||||||||||||||||||
Last Modified: | 09 Mar 2020 13:19 |
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