A Lighthouse Beacon from the Core of an Active Galaxy 

[Right] - A NASA Hubble Space Telescope (HST) view of the core of the
barred spiral Seyfert galaxy NGC 5728 reveals a spectacular bi-conical
beam of light that is ionizing the gas in the central region of the
galaxy.

This image was presented at the American Astronomical Society meeting
in Berkeley, California by Dr. Andrew Wilson of the Space Telescope
Science Institute (STScI), Baltimore, Maryland.

Because NGC 5728 is an active galaxy, the core might contain a super
massive black hole surrounded by a disk of gas, according to
astronomers. This hot disk glows with ultraviolet light.  However, a
dense ring of gas blocks Hubble's view of the black hole and glowing
accretion disk. The visible and ultraviolet light escapes along the
open ends of the gas "donut" to several thousands of light-years from
the nucleus.  The ring thus shapes the escaping ultraviolet light into
two lighthouse beacon style "ionization cones."

The image was made September 4, 1992 with the Wide Field and Planetary
Camera (WFPC) in PC mode. Exposures were obtained in the light of
doubly-ionized oxygen and neutral hydrogen.

Credit: Andrew S. Wilson (STScI)/NASA
Co-investigators: James A. Braatz (Univ. Of Maryland), 
Timothy M. Heckman (STScI), Julian H. Krolik (JHU), and 
George K. Miley (Leiden Observatory). 


[Left] - A ground based image of the barred spiral galaxy NGC 5728,
located 125 million light-years away in the constellation Libra.

Courtesy: Allan Sandage, Carnegie Observatories 


PHOTO CATPION NO.:  STScI-PRC93-15