header graphic



[*] Research on black holes
van der Marel R.P.
in the Space Telescope Science Institute Annual Report, p. 17, 1998
© 1999. Association of Universities for Research in Astronomy. All Rights Reserved.

By allowing scientists to peer into the highly energetic centers of galaxies, Hubble continues to make ground-breaking contributions in the study of black holes. For several decades scientists have known from observations across the electromagnetic spectrum that some galaxies have extremely active regions in their cores. They have long believed that this activity is due to the accretion of matter onto massive black holes.

One of the most enigmatic active galaxies is Centaurus A, fascinating because it exhibits a strong radio source. The galaxy has an impressive band of dust, gas, and young stars that crosses the optical image, especially in observations taken by WFPC2. It is believed to be a remnant of a merger between a large elliptical galaxy and a small spiral galaxy. The strong dust absorption had previously prevented Hubble from obtaining an unobscured view of the very central region; however, new observations with NICMOS have unveiled the galaxy's center. The observation revealed the existence of a small nuclear disk of hydrogen gas, but surprisingly this small disk is not aligned with any of the radio features from the black hole. The merger is likely to have contributed to the peculiar twisting in the interior parts of Centaurus A.

In related studies, Hubble has provided detailed diagnostic information for several other galaxies, including NGC 7052. Using FOS, observers discovered that the gas inside this galaxy is rotating rapidly. A direct calculation of the mass of the black hole at the center of NGC 7052 turns out to be 300 million times that of the sun. Accumulating evidence now suggests that all galaxies may have black holes in their centers, and that the normal galaxies of today once made up the luminous quasar population of the early universe.

Arrow Return to my bibliography.              Home Return to my home page.

Last modified April 22, 1999.
Roeland van der Marel, marel@stsci.edu.
Copyright Notice.