RXTE Discoveries

Winners of 2001 Rossi Prize Named for Black Hole Discovery - January 2001

by Christopher Wanjek

Two astronomers who first observed X-ray light being stretched by the crushing force of gravity near supermassive black holes are the winners of the 2001 Bruno Rossi Prize, awarded by the High Energy Astrophysics Division of the American Astronomical Society.

The work of Prof. Andrew Fabian, of the Institute of Astronomy in Cambridge, England, and Prof. Yasuo Tanaka, of the Institute for Space and Astronautical Science in Kanagawa, Jfapan, is a confirmation of Einstein's theory of general relativity, which postulates that mass curves the fabric of spacetime and therefore the path of light. Black holes, the source of extreme mass and gravity, provide a convenient laboratory to observe this phenomenon.

The astronomers' observation also provided the closest glimpse yet of a black hole, a region in space where nothing, not even light, can escape once it crosses a theoretical border known as the event horizon.

The Rossi Prize recognizes significant contributions as well as recent and original work in high-energy astrophysics. It is awarded annually in honor of the late Professor Bruno Rossi, an authority of cosmic rays whose experimental techniques at the Los Alamos Laboratory and at MIT gave birth to the field of X-ray astronomy. The prize also includes an engraved certificate and a $1,500 award.

"I am of course delighted by the award and honored to share it with Yasuo Tanaka," said Prof. Fabian. "Very many people have been involved in the success of ASCA mission, which made testing our prediction possible, and we owe them many thanks."

"I view this distinction as a recognition of the achievements of the ASCA mission, in which I am deeply involved," said Prof. Tanaka, currently a visiting scientist at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. "I am indebted to all the young collaborators who have made this work together."

Profs. Fabian and Tanaka's discovery was made the Advanced Satellite for Cosmology and Astrophysics (ASCA), a joint Japanese-U.S. mission. Turning this X-ray telescope to several galaxies with extremely bright central regions (known as active galactic nuclei), the two scientists observed broad iron K-lines.This is a term that refers to the light signature, or spectrum, of hot iron atoms that is broadened or stretched by the tug of gravity. The observation is a strong indication that a black hole is powering the fantastic light show in the galaxy core.

Profs. Fabian and Tanaka are invited to deliver the Rossi Prize Lecture at the January 2002 meeting of the American Astronomical Society, held January 6-10, 2002, in Washington, DC.


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