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CAS professor detects supermassive black hole

This story was published in the BU Bridge on January 21, 2005.

A team of astronomers that includes Elizabeth Blanton, a CAS assistant professor of astronomy, has detected and measured the most powerful outburst known in the universe. Using data from NASA’s Chandra X-ray Observatory, it was discovered in a distant cluster of galaxies and is associated with what the researchers describe as a voracious supermassive black hole.

Chandra images reveal two cavities in the X-ray emission from the galaxy cluster, each 650,000 light-years across, that appear to have been created by jets of energy emitted from the black hole, an object a billion times more massive than our sun. Each cavity is filled with extremely high-energy electrons that emit the radio waves that were detected by the National Radio Astronomy Observatory’s Very Large Array, one of the world’s premier astronomical observatories, in Socorro, N.M.

Although black holes swallow energy, and this one is characterized by the researchers as voracious, they also violently eject powerful jets of high-energy particles. By calculating the density, temperature, and pressure of the X-ray-emitting hot gas surrounding the cavities created by the jets, the researchers were able to estimate how much energy was ejected to create the cavities. Using the standard estimate that about 10 percent of the gravitational energy of a black hole is used to launch the jets, they then estimated how much the black hole had swallowed: the mass of almost 300 million suns — a staggering figure.

According to the researchers, this outburst has been pushing gas away from the black hole at supersonic speeds for more than 100 million years. They estimate that the mass of the displaced gas is more than the mass of all the stars in the Milky Way.

The continuing activity of the black hole, say the scientists, may be preventing the formation of new stars, a process that depends on the cooling and coalescing of gas in a galaxy.

Blanton’s collaborators on the project are lead author Brian McNamara of Ohio University in Athens, Ohio, Paul Nulsen of the Harvard-Smithsonian Center for Astrophysics, and colleagues at the MIT Center for Space Research, the National Radio Astronomy Observatory in Socorro, and the astronomy department at the University of Virginia in Charlottesville.

The research was published in the January 6, 2005, edition of the journal Nature. Images of the eruption can be seen at http://chandra.harvard.edu/photo/2005/ms0735.