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Earth-sized telescope finds clue to black hole growth

December 3, 2015
Perimeter Institute for Theoretical Physics
For the first time, astronomers have detected evidence of magnetic fields near Sagittarius A, the black hole at the center of the Milky Way, taking the study of black hole growth from theoretical expectation to empirical fact.

Artist's impression of galaxy with black hole (stock image).
Credit: © sakkmesterke / Fotolia

A new discovery, published today in the journal Science, has greatly deepened our understanding black holes, which are believed to be the gravitational engines at the centres of most galaxies, including our own.

Using an array of telescopes that spans the globe, astronomers detected evidence of magnetic fields near Sagittarius A*, the 4.5-million-solar-mass black hole at the centre of the Milky Way.

Decades of theoretical work, including enormous computer simulations, have painted a picture of how strong horizon-scale magnetic fields near the black hole contribute to its growth. Now that this international collaboration has discovered high levels of polarization in the radio emissions from Sagittarius A*, physicists have proof that these magnetic fields indeed exist.

Were these magnetic fields not there, "a lot theoretical astrophysics would have to go back to the drawing board," says Avery Broderick, an Associate Faculty member at Perimeter Institute for Theoretical Physics, jointly appointed at the University of Waterloo.

Researchers achieved this new finding using the Event Horizon Telescope -- an interconnected array of millimeter-wavelength telescopes located around the world. Together, they form an Earth-sized telescope capable of extremely high resolution, which, in the near future, will enable astronomers to image the event horizon of a black hole for the first time in human history.

"There are now enough telescopes in the array, in principle, to make images in the next couple of years," Broderick added. "This might be the point, like the turn of the last century, when all of a sudden the puzzle pieces click into place."

Those images will enable astrophysicists to transform our understanding of how black holes grow, how they interact with their surroundings, and even the nature of gravity.

"We are on the cusp of a true first in astronomical exploration," says Avery Broderick. "We fully expect to have imaged a black hole's event horizon in a matter of years. This would be an incredible accomplishment, not just for science, but humankind."

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Journal Reference:

  1. M. D. Johnson, V. L. Fish, S. S. Doeleman, D. P. Marrone, R. L. Plambeck, J. F. C. Wardle, K. Akiyama, K. Asada, C. Beaudoin, L. Blackburn, R. Blundell, G. C. Bower, C. Brinkerink, A. E. Broderick, R. Cappallo, A. A. Chael, G. B. Crew, J. Dexter, M. Dexter, R. Freund, P. Friberg, R. Gold, M. A. Gurwell, P. T. P. Ho, M. Honma, M. Inoue, M. Kosowsky, T. P. Krichbaum, J. Lamb, A. Loeb, R.-S. Lu, D. MacMahon, J. C. McKinney, J. M. Moran, R. Narayan, R. A. Primiani, D. Psaltis, A. E. E. Rogers, K. Rosenfeld, J. SooHoo, R. P. J. Tilanus, M. Titus, L. Vertatschitsch, J. Weintroub, M. Wright, K. H. Young, J. A. Zensus, L. M. Ziurys. Resolved magnetic-field structure and variability near the event horizon of Sagittarius A. Science, 2015; 350 (6265): 1242 DOI: 10.1126/science.aac7087

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Perimeter Institute for Theoretical Physics. "Earth-sized telescope finds clue to black hole growth." ScienceDaily. ScienceDaily, 3 December 2015. <>.
Perimeter Institute for Theoretical Physics. (2015, December 3). Earth-sized telescope finds clue to black hole growth. ScienceDaily. Retrieved May 28, 2017 from
Perimeter Institute for Theoretical Physics. "Earth-sized telescope finds clue to black hole growth." ScienceDaily. (accessed May 28, 2017).