Prof. Ramesh Narayan

Ramesh Narayan

Thomas Dudley Cabot Research Professor of the Natural Sciences

Harvard University

Center for Astrophysics (CfA), Harvard & Smithsonian

Ramesh Narayan is a theoretical and computational astrophysicist who has carried out research in many areas within the field of high energy astrophysics. Topics he has explored in depth include accretion disks, active galactic nuclei, black holes, gamma-ray bursts, gravitational lensing, image processing, interstellar scintillation, magnetic reconnection, neutron stars, pulsars, quasars, relativistic jets, shocks, X-ray binaries, X-ray bursts, very long baseline interferometry, white dwarfs. Black hole accretion has been a central thread in his research for many decades.

Narayan is a physicist by training, who earned all his degrees in India: B.Sc. from Madras University, M.Sc. and Ph.D. (advisor: Professor S. Ramaseshan) from Bangalore University. After spending a few years at the Raman Research Institute, Bangalore, he went to Caltech in 1983 as a postdoctoral fellow, where he had the good fortune to work with two modern giants of theoretical astrophysics: Professor Roger Blandford and Professor Peter Goldreich. He then became a faculty member in the Department of Astronomy, University of Arizona, Tucson, before moving in 1991 to Harvard University as a Professor in the Department of Astronomy. He retired from the Harvard teaching faculty in 2026, but continues on as the Thomas Dudley Cabot Research Professor of the Natural Sciences. He is one of the Principal Investigators at the Harvard Black Hole Initiative (BHI). Additional details of Narayan's professional career can be found here.

Narayan was a key member of the Event Horizon Telescope (EHT) Collaboration, which obtained the first direct images of two black holes: the 6.5 billion solar mass black hole M87* at the center of the giant elliptical galaxy Messier 87 (the EHT image of M87* was announced to the public on April 10, 2019), and the 4.1 million solar mass black hole Sagittarius A* (Sgr A) at the center of our own Milky Way Galaxy (May 12, 2022). The ring-like morphology of the EHT images of M87 and Sgr A* confirms the presence of a dark central region, called the shadow of a black hole, as predicted by general relativity. The EHT observations further show that the gas accreting on these two black holes is incredibly hot (well over 10 billion degrees Kelvin) and strongly magnetized, confirming ideas on hot advection-dominated accretion flows (ADAFs) developed by Narayan and his collaborators in the 1990s and early 2000s (see this short review for an EHT-focused discussion, or the following longer review of hot accretion flow models). EHT observations have also tightened the evidence for Sgr A* being a true black hole, with an event horizon (see Section 4 of this paper, or the longer discussion here).

Narayan was elected a Member of the National Academy of Sciences in 2013. He was also elected Fellow of the Royal Society (London, 2006), the American Association for the Advancement of Science (2010), The World Academy of Sciences (2015), and the American Academy of Arts and Sciences (2026), and Honorary Fellow of the Indian Academy of Sciences (2016).

A historic moment! On July 24, 2018, four sub-groups of the Event Horizon Telescope Collaboration (EHTC), who until then had worked independently to convert EHT measurements to their own individual images of the M87 black hole, came together at the Black Hole Initiative (BHI), Harvard University, to compare each others' results. The excellent agreement of the four independently generated images was celebrated by the assembled scientists in this photograph taken in the basement of the BHI building. The image projected on the screen is an average of the four groups' results. The Director of the EHT, Sheperd Doeleman, is at the far right. It took the EHTC another 8+ months to tie up all the details before announcing the first image of a black hole to the public.

April 10, 2019: A historic day! On this day, in a series of coordinated press releases around the world and six professional publications (1 2 3 4 5 6), the EHTC announced the first astronomical image ever of a black hole, that of M87* at the center of the galaxy M87. This photograph was taken during a celebration at Smithsonian's National Air and Space Museum in Washington, DC.

May 12, 2022: On this day, the EHTC released the image of the black hole Sagittarius A* (Sgr A*) at the center of our Milky Way Galaxy, and published the details of the research in six professional publications: 1 2 3 4 5 6. This group photograph was taken on the grounds of Smithsonian's Washington DC National Mall campus, with the Smithsonian Castle as backdrop.

May 12, 2022: Following the EHTC announcement of the image of Sgr A*, this group photograph was taken at a reception inside the Smithsonian Castle. The image in the background is that of M87*.

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