Dr. Tim Johannsen, Astrophysicist

Contact: tjohannsen@uwaterloo.ca

Interests: black hole astrophysics, tests of general relativity

Publications:     ADS       ARXIV       INSPIRE

For an overview, see my invited review articles Sgr A* and General Relativity and Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum.


In the News

Do Black Holes Really Have No Hair?,” by Tim Johannsen, CQG+ (2016)

The Death of General Relativity Lurks in a Black Hole’s Shadow,” by Lizzie Wade, Wired (2016)

The Black Hole Test” by D. Psaltis and S. Doeleman, Scientific American, 313, 3, 74 (2015)

Verdrehtes Licht von rotierenden Schwarzen Löchern” by H. Falcke, Physik Journal, 10, 4, 18 (2011)

Black Hole Silhouettes”  by C. Petit, Science News, 178, 8, 22 (2010)

12 events that will change everything” by G. Musser, Scientific American, 302, 6, 39 (2010)

Hunting Hidden Dimensions - Black holes, giant and tiny, may reveal new realms of space” by D. Steele, Science News, 176, 7, 22 (2009)


Press Releases

Testing General Relativity with Black Holes,” Perimeter Institute (2016)

Putting Einstein’s Theory of General Relativity to the Test,” University of Waterloo (2016)

Preparing for a Cosmological Challenge,  Perimeter Institute (2016)

Could Black Holes have Hair?,  Perimeter Institute (2014)


Science Blogs

Testing General Relativity with Black Holes,” 3tags.org, September 14, 2016

Testing General Relativity with Black Holes,” DeepStuff.org, September 14, 2016

A Research Team led by the Perimeter Institute Has Demonstrated a New Method to Test General Relativity Using Black Holes,” SPACEREF Canada, September 13, 2016

La Primera Imagen de Sagitario A* Podría Ser la Prueba “Definitiva” de la Relatividad General,” Cuaderno de Cultura Científica, January 28, 2016

Preparing for a Cosmological Challenge,  DeepStuff.org, January 20, 2016

Synopsis: Testing General Relativity in a Black Hole’s Shadow,” APS Physics, January 19, 2016

Hairless Black Holes,” SmallerQuestions.org, October 12, 2011

Do Black Holes Generate a Ring of Light? Experts Say "Yes",” The Daily Galaxy, May 18, 2010

Black Holes Should Generate Ring of Light, Say Astronomers,” MIT Technology Review, May 14, 2010


Testing the No-Hair Theorem with Iron Lines

Johannsen & Psaltis (2011) constructed a Kerr-like metric that depends on an additional parameter, which measures potential deviations from the Kerr metric.

Johannsen & Psaltis (2013) simulated iron line profiles in this metric, demonstrating that this method can be used to test the no-hair theorem.

A selection of iron line profiles is available for download here.