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EMBARGOED UNTIL: 1:00 a.m. (EST) November 30, 2000

PHOTO NO.: STScI-PRC00-37


HUBBLE CAPTURES AN EXTRAORDINARY AND POWERFUL ACTIVE GALAXY

Resembling a swirling witch's cauldron of glowing vapors, the black
hole-powered core of a nearby active galaxy appears in this colorful
NASA Hubble Space Telescope image. The galaxy lies 13 million
light-years away in the southern constellation Circinus.

This galaxy is designated a type 2 Seyfert, a class of mostly spiral
galaxies that have compact centers and are believed to contain massive
black holes. Seyfert galaxies are themselves part of a larger class of
objects called Active Galactic Nuclei or AGN. AGN have the ability to
remove gas from the centers of their galaxies by blowing it out into
space at phenomenal speeds. Astronomers studying the Circinus galaxy are
seeing evidence of a powerful AGN at the center of this galaxy as well.

Much of the gas in the disk of the Circinus spiral is concentrated in
two specific rings -- a larger one of diameter 1,300 light-years, which
has already been observed by ground-based telescopes, and a previously
unseen ring of diameter 260 light-years.

In the Hubble image, the smaller inner ring is located on the inside of
the green disk. The larger outer ring extends off the image and is in
the plane of the galaxy's disk. Both rings are home to large amounts of
gas and dust as well as areas of major "starburst" activity, where new
stars are rapidly forming on timescales of 40 - 150 million years, much
shorter than the age of the entire galaxy.

At the center of the starburst rings is the Seyfert nucleus, the
believed signature of a supermassive black hole that is accreting
surrounding gas and dust. The black hole and its accretion disk are
expelling gas out of the galaxy's disk and into its halo (the region
above and below the disk). The detailed structure of this gas is seen
as magenta-colored streamers extending towards the top of the image.

In the center of the galaxy and within the inner starburst ring is a
V-shaped structure of gas. The structure appears whitish-pink in this
composite image, made up of four filters. Two filters capture the narrow
lines from atomic transitions in oxygen and hydrogen; two wider filters
detect green and near-infrared light. In the narrow-band filters, the
V-shaped structure is very pronounced. This region, which is the
projection of a three-dimensional cone extending from the nucleus to the
galaxy's halo, contains gas that has been heated by radiation emitted by
the accreting black hole. A "counter-cone," believed to be present, is
obscured from view by dust in the galaxy's disk. Ultraviolet radiation
emerging from the central source excites nearby gas causing it to glow.
The excited gas is beamed into the oppositely directed cones like two
giant searchlights.

Located near the plane of our own Milky Way Galaxy, the Circinus galaxy
is partially hidden by intervening dust along our line of sight. As a
result, the galaxy went unnoticed until about 25 years ago. This Hubble
image was taken on April 10, 1999 with the Wide Field Planetary
Camera 2.

The research team, led by Andrew S. Wilson of the University of
Maryland, is using these visible light images along with near-infrared
data to further understand the dynamics of this powerful galaxy.

Credits: NASA, Andrew S. Wilson (University of Maryland); Patrick L.
Shopbell (Caltech); Chris Simpson (Subaru Telescope); Thaisa
Storchi-Bergmann and F. K. B. Barbosa (UFRGS, Brazil); and Martin J.
Ward (University of Leicester, U.K.)

EDITOR'S NOTE: Image files and additional information are available at:
http://oposite.stsci.edu/pubinfo/pr/2000/37 or links in
http://oposite.stsci.edu/pubinfo/latest.html
http://oposite.stsci.edu/pubinfo/pictures.html or
http://hubble.stsci.edu/go/news

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