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Office of Public Affairs
Yale University

CONTACT:
Jacqueline Weaver, 203-432-8555 #166

For Immediate Release: May 26, 2003

Grand Unification Theory of Galaxies Outlined

New Haven, Conn. -- Despite a decade of efforts to find flaws in the
unification theory of active galaxies, the theory correctly explains
the exotic phenomena of accreting supermassive black holes, a Yale
astronomer said today. 

"Furthermore, the striking parallels between normal and active
galaxies that have become apparent in the last few years," said Meg
Urry, professor of physics at Yale and director of the Yale Center
for Astronomy and Astrophysics, "suggest that there is a larger '
Grand Unification' at play. Apparently every galaxy goes through an
active phase." 

Urry spoke at the American Astronomical Society meeting in Nashville,
Tenn. 

Urry said the Grand Unification theory predicts what objects should
appear in very deep multi-wavelength views of the universe. "Most of
the active galaxies in the early universe have been hidden from view
until now," she said. "We predict there are far more hidden black
holes than brightly shining active galaxies."

New multi-wavelength surveys involving unique space observatories
provide a way to test the Grand Unification theory, she said. Three
of the National Aeronautics and Space Administration (NASA) space
observatories -- the Hubble Space Telescope and the Chandra X-Ray
Observatory, both already in orbit, and the Space Infrared Telescope
Facility, due to be launched in August -- are critically important
because they allow very deep imaging from far-infrared to X-ray
wavelengths, where active galaxies and star-forming galaxies radiate
most of their energy. Preliminary results from the first two
observatories are encouraging.

"The new challenge is to understand in detail how galaxy formation --
the gravitational collapse of a galaxy -- is tied to star formation
in that galaxy and to accretion onto the black hole at its center,"
she said. "Now we think all these processes are happening
simultaneously, in the same objects. As a galaxy forms and collapses
under the weight of its own gravity, it stimulates both intense star
formation and the dumping of gas and stars onto the seed black hole
at the center of the gravitational potential well."

"The galaxy starts collapsing, makes stars and makes an active
nucleus," Urry said. "The violent events of this collapse dump matter
onto the black hole and this releases a lot of energy. All these wild
things are happening at once." 

# # #

EDITORS: A cartoon illustrating the unification paradigm for active
galaxies (not to scale), is available at

http://www.yale.edu/opa/assets/images/releases/20030520_cover.jpg

It shows the supermassive black hole and the accretion disk (pink) of
matter falling toward the black hole. PHOTO CREDIT: Meg Urry (Yale)
and John Godfrey (STScI). Copyright PASP, reprinted by permission of
the author. This photograph can be obtained after 4:30 P.M. EST, May
26, 2003.

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