Science / Medicine : Quasars ‘Buried’ in Galaxies

Five relatively close galaxies appear to harbor buried quasars deep within their cores, Caltech astronomers reported last week at a meeting of the American Astronomical Society in Seattle. The quasars--the brightest, most energetic objects in the universe, and also the most distant objects known--are hidden from view because they are enshrouded by thick, doughnut-shaped clouds of dust, astronomer S. George Djorgovski said. The results provide considerable support for “grand unified” quasar theories, Djorgovski said.

While quasars are about the size of our solar system, they outshine entire galaxies containing hundreds of billions of stars. One problem in the study of quasars is that observers see a bewildering variety of quasars, active galaxies and related objects in the celestial sky. Some, for example, emit visible light, while others emit radiation at radio frequencies. Grand unified theories of active galactic nuclei state that much of this diversity is the result of different viewing angles.

The Caltech group examined eight galaxies that have strong radio emissions, suggesting the presence of quasars. The found that five of the galaxies had very strong infrared emissions, indicating the presence of a bright central quasar heating up the gas surrounding it. That gas prevents the astronomers from seeing the quasars at normal wavelengths of light, but the underlying quasar must be very similar to those that can be seen from Earth, Djorgovski said.