Press Release

Astronomers use Chandra to study nearby galaxy

By SpaceRef Editor
August 8, 2001
Filed under , ,

First observed by Chandra in September 1999, Centaurus A was an early
demonstration of the spectacular science this powerful X-ray observatory could
do. Astronomers continue to use Chandra to study this elliptical galaxy (also
known as NGC 5128) that contains a spectacular jet and a core teeming with
X-ray emitting sources.

This Chandra image of Cen A shows a bright central source: the Active Galactic
Nucleus (AGN) suspected of harboring a supermassive black hole. Chandra also
detects a jet emanating from the core and numerous point-like X-ray sources,
all bathed in diffuse X-rays produced by several-million-degree gas that fills
the galaxy. A team of scientists, led by Ralph Kraft of the Smithsonian
Astrophysical Observatory, has begun to study each of these components of
X-ray emission from Cen A. The unprecedented imaging resolution of Chandra
allows scientists for the first time to clearly resolve each of these distinct
components of the X-ray emission for detailed study.

Over 200 point-like X-ray sources have been identified and studied in Cen A.
Because of their distribution around the center of the galaxy, it is believed
that most of these sources are X-ray binaries in which a neutron star or
stellar-sized black hole is accreting matter from a nearby companion star. A
few may be supernova remnants or unrelated, more distant background galaxies.
Comparison of Cen A’s X-ray binary population with populations in other
galaxies is important for understanding the evolutionary history of galaxies.
It is becoming clear that there are significant variations in the X-ray
binary populations of otherwise similar galaxies. The reason for this is
uncertain, but may be related to differences in the star formation history
or mechanisms for the creation of X-ray binaries. The observation of the jet
has provided scientists some surprises as well. The X-ray structure of the
jet has been shown to be significantly different than the radio structure,
and the X-ray jet is much more uneven than originally believed. These results
have cast doubts on simple models of how the energetic particles ejected
from the active nucleus travel along the jet.

The Cen A image was created from Chandra observations taken on December 5,
1999 (35,900 seconds) and May 17, 2000 (36, 500 seconds) with the Advanced
CCD Imaging Spectrometer (ACIS) as part of the HRC GTO program. Other
members of this research team include Steve Murray (PI), Bill Forman, and
Christine Jones (Smithsonian Astrophysical Observatory), Martin Hardcastle
and Diana Worrall (Bristol University UK), and Julia Kregenow (Wittenberg

Credit: NASA/SAO/R.Kraft et al.

Scale: Image is 6 x 10 arcmin.

[NOTE: Additional images are available at]

SpaceRef staff editor.